UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K/A

Amendment No. 1

ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF

THE SECURITIES EXCHANGE ACT OF 1934

CHURCH & DWIGHT CO., INC.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (609) 683-5900

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15 (d) of the Securities Exchange Act of 1934 during the preceding 12 months and (2) has been subject to such filing requirements for the past 90 days.  Yes  x    No  ¨

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K.  ¨

Indicate by check mark whether the registrant is an accelerated filer (as defined in Rule 12b-2 of the Act).  Yes  x    No  ¨

The aggregate market value of the voting and non-voting common equity held by non-affiliates as of July 2, 2004 (the last business day of the registrant’s most recently completed second fiscal quarter) was approximately $1,659 million. For purposes of making this calculation only, the registrant included all directors, executive officers and beneficial owners of more than ten percent of the Common Stock of the Company as affiliates. The aggregate market value is based on the closing price of such stock on the New York Stock Exchange on July 2, 2004.

As of March 8, 2005, 63,378,667 shares of Common Stock were outstanding.

Documents Incorporated by Reference

Certain provisions of the registrant’s definitive proxy statement to be filed not later than April 30, 2005 are incorporated by reference in Items 10 through 14 of Item III of this Annual Report on Form 10-K.

EXPLANATORY NOTE

Church & Dwight Co., Inc. is filing this amendment on Form 10-K/A to its Form 10-K for the year ended December 31, 2004 solely to correct three typographical errors contained in note 19 (Unaudited Quarterly Financial Information) to Church & Dwight’s consolidated financial statements, which are included in Item 8 of the Form 10-K. The corrections relate to the amounts of basic net income per share in the second quarter of 2004 and diluted net income per share in the first and second quarters of 2004. The Form 10K/A does not otherwise amend the Form 10-K.

ITEM 8. FINANCIAL STATEMENTS AND SUPPLEMENTARY DATA

CHURCH & DWIGHT CO., INC. AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF INCOME

See Notes to Consolidated Financial Statements.

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CHURCH & DWIGHT CO., INC. AND SUBSIDIARIES

CONSOLIDATED BALANCE SHEETS

See Notes to Consolidated Financial Statements.

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CHURCH & DWIGHT CO., INC. AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF CASH FLOW

See Notes to Consolidated Financial Statements.

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CHURCH & DWIGHT CO., INC. AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY

Years ended December 31, 2004, 2003 and 2002

See Notes to Consolidated Financial Statements.

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CHURCH & DWIGHT CO., INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

1. Accounting Policies

Business

The Company develops, manufactures and markets a broad range of consumer and specialty products. It sells its products, primarily under the ARM & HAMMER and TROJAN brand names, to consumers through supermarkets, drug stores and mass merchandisers; and to industrial customers and distributors.

Basis of Presentation

The accompanying Consolidated Financial Statements are presented in accordance with accounting principles generally accepted in the United States of America. The accompanying Consolidated Financial Statements include the accounts of the Company and its majority-owned subsidiaries. The Company accounts for equity investments on the cost method for those investments in which it does not control nor have the ability to exert significant influence over the investee, which is generally when the Company has less than a 20 percent ownership interest. In circumstances where the Company has greater than a 20 percent ownership interest and has the ability to exercise significant influence but does not control the investee, the investment is accounted for under the equity method. As a result, the Company accounts for its less than 20% interest in USA Metro, Inc. on the cost basis and accounts for its 50% interest in its Armand Products Company joint venture (“Armand”) and the ArmaKleen Company joint venture (“ArmaKleen”) under the equity method of accounting. Both Armand and ArmaKleen companies are specialty chemical companies and the Company’s portion of their equity earnings is included in the corporate segment in Note 17. Neither company is considered a significant subsidiary; therefore, summarized financial statement data is not presented. On May 28, 2004, the Company purchased the remaining 50% ownership interest of Armkel, LLC (“Armkel”) that it did not own from affiliates of Kelso & Company (“the Armkel acquisition”) for a purchase price of $262 million and Armkel was merged into the Company. Results of operations for the business are included in the Company’s consolidated financial statements from May 29, 2004. Prior to May 28, 2004, the Company accounted for its investment in Armkel under the equity method. All material intercompany transactions and profits have been eliminated in consolidation.

Fiscal Calendar

The Company’s fiscal year begins on January 1 of the year stated and ends on December 31. Quarterly periods are based on a 4-4-5 methodology (4 weeks-4 weeks-5 weeks). As a result, the first quarter can include a partial or expanded week in the first four week period of the quarter. Similarly, the last five week period in the fourth quarter could include a partial or expanded week.

Use of Estimates

The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent gains and losses at the date of the financial statements and reported amounts of revenue and expenses during the reporting period. Management makes estimates regarding inventory valuation, promotional and sales returns reserves, the carrying amount of goodwill and other intangible assets, the realization of deferred tax assets, tax reserves, liabilities related to pensions and other postretirement benefit obligations and other matters that affect the reported amounts and other disclosures in the financial statements. Estimates by their nature are based on judgment and available information. Therefore, actual results could differ materially from those estimates, and it is possible that changes in such estimates could occur in the near term.

Revenue Recognition

Revenue is recognized when finished goods are delivered to our customers or when finished goods are picked up by a customer’s carrier.

Promotional and Sales Returns Reserves

The Company conducts extensive promotional activities, primarily through the use of off-list discounts, slotting, co-op advertising, periodic price reduction arrangements, and end-aisle and other in-store display. All such costs are netted against sales. Slotting costs are recorded when the related sale is recognized. Co-op advertising costs are recorded when the customer places the advertisement for the Company’s products. Discounts relating to price reduction arrangements are recorded when the related sale takes place. Costs associated with end-aisle or other in-store displays are recorded when product is sold relating to the promotion. The reserves for sales returns and consumer and trade promotion liabilities are established based on the Company’s best estimate of the amounts necessary to settle future and existing obligations for such items on products sold as of the balance sheet date. The Company uses historical trend experience and coupon redemption provider input in arriving at coupon reserve requirements, and forecasted appropriations, customer and sales organization inputs, and historical trend analysis in arriving at the reserves required for other promotional activities and sales returns. While the Company believes that promotional and sales returns reserves are adequate and that the judgment applied is appropriate, amounts estimated to be due and payable could differ materially from actual costs incurred in the future.

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Cost of Sales, Marketing and Selling, General and Administrative Expenses

Cost of sales includes costs related to the manufacture of the Company’s products (including raw material costs, inbound freight costs, direct labor, and indirect plant costs such as plant supervision, receiving, inspection, maintenance labor and materials, depreciation, taxes and insurance), purchasing, production planning, operations management, logistics, freight to customers, warehousing costs and internal transfer freight costs.

Marketing expenses include costs for advertising (excluding the costs of co-op advertising programs, which are reflected in net sales), costs for coupon insertion (mainly the cost of printing and distribution), consumer promotion costs (such as on-shelf advertisements and floor ads), public relations, package design expense and market research costs.

Selling, general and administrative expenses include costs related to functions such as sales, corporate management, marketing administration and legal, among others. Such costs include compensation related costs (such as benefits, profit sharing, deferred compensation and employer contributions to the 401K savings plan); travel and entertainment related expenses; trade show expenses; insurance; professional and other consulting fees; costs related to temporary staff; staff relocation costs; and non-capitalizable software related costs.

Impairment of Long-lived Assets

Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. In such situations, long-lived assets are considered impaired when estimated future cash flows (undiscounted and without interest charges) resulting from the use of the asset and its eventual disposition are less than the asset’s carrying amount. While the Company believes that its estimates of future cash flows are reasonable, different assumptions regarding such cash flows could materially affect its estimates. When an impairment is indicated, the estimated future cash flows are then discounted to determine the estimated fair value of the asset and an impairment charge is recorded for the difference between the carrying value and the net present value of estimated future cash flows.

Foreign Currency Translation

Financial statements of foreign subsidiaries are translated into U.S. dollars in accordance with Statement of Financial Accounting Standards (SFAS) No. 52. Unrealized gains and losses are recorded in Accumulated Other Comprehensive Loss. Gains and losses on foreign currency transactions were recorded in the accompanying Consolidated Statements of Income.

Cash Equivalents

Cash equivalents consist of highly liquid short-term investments, which mature within three months of purchase.

Inventories

Inventories are valued at the lower of cost or market. Approximately 31% and 45% of the inventory at December 31, 2004 and 2003, respectively, were determined utilizing the last-in, first-out (LIFO) method. The cost of substantially all inventory in the Company’s Specialty Products segment as well as inventory sold under the ARM & HAMMER and BRILLO trademarks in the Consumer Domestic segment is determined utilizing the LIFO method. The cost of the remaining inventory is determined using the first-in, first-out (FIFO) method. When appropriate, the Company writes down the carrying value of its inventory to the lower of cost or market (net realizable value), including any costs to sell or dispose the adjusted inventory. The Company identifies any slow moving, obsolete or excess inventory to determine whether a valuation allowance is indicated. The determination of whether inventory items are slow moving, obsolete or in excess of needs requires estimates and assumptions about the future demand for the Company’s products, technological changes, and new product introductions. The estimates as to the future demand used in the valuation of inventory are dependent on the ongoing success of the Company’s products. In addition, the Company’s allowance for obsolescence may be impacted by the rationalization of the number of stock keeping units. To minimize this risk, the Company evaluates its inventory levels and expected usage on a periodic basis and records adjustments as required. Adjustments to reduce the inventory’s net realizable value were $5.9 million at December 31, 2004, and $3.2 million at December 31, 2003.

Property, Plant and Equipment

Property, plant and equipment and additions thereto are stated at cost. Depreciation is recorded using the straight-line method over the estimated useful lives of the respective assets. Estimated useful lives for building and improvements, machinery and equipment, and office equipment range from 9-40, 3-20, and 3-10 years, respectively. Routine repairs and maintenance are expensed when incurred. Leasehold improvements are depreciated over the lease term, except when the lease renewal has been determined to be reasonably assured and failure to renew the lease imposes a penalty on the Company.

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Property, plant and equipment are reviewed periodically for possible impairment in accordance with SFAS No. 144, “Accounting for the Impairment or Disposal of Long-Lived Assets”. The Company’s impairment review is based on an undiscounted cash flow analysis at the lowest level for which identifiable cash flows exist. The analysis requires management judgment with respect to changes in technology, the continued success of product lines, and future volume, revenue and expense growth rates. The Company conducts annual reviews for idle and underutilized equipment, and reviews business plans for possible impairment implications. Impairment occurs when the carrying value of the asset exceeds the future undiscounted cash flows. When an impairment is indicated, the estimated future cash flows are then discounted to determine the estimated fair value of the asset and an impairment charge is recorded for the difference between the carrying value and the net present value of estimated future cash flows.

Software

The Company accounts for software in accordance with Statement of Position (SOP) 98-1 “Accounting for the Costs of Computer Software Developed or Obtained for Internal Use.” SOP 98-1 requires companies to capitalize certain costs of developing computer software. Amortization is recorded using the straight-line method over the estimated useful lives of the software, which is estimated to be 5 years.

Long-Term Supply Contracts

Long-term supply contracts represent advance payments made by the Company under multi-year contracts with suppliers of raw materials and finished goods inventory. Such advance payments are applied over the lives of the contracts using the straight-line method.

Derivatives

All derivatives are recognized as assets or liabilities at fair value in the accompanying Consolidated Balance Sheets.

Derivatives designated as hedges are either (1) a hedge of the fair value of a recognized asset or liability (“fair value” hedge), or (2) a hedge of the variability of cash flows to be received or paid related to a recognized asset or liability (“cash flow” hedge).

Goodwill and Other Intangible Assets

The Company accounts for Goodwill and Other Intangible Assets in accordance with SFAS No. 142. Under SFAS No. 142, goodwill and intangible assets with indefinite useful lives are not amortized but are reviewed for impairment at least annually. Intangible assets with finite lives are amortized over their estimated useful lives using the straight-line method.

Research and Development

Research & development costs in the amount of $33.0 million in 2004, $26.9 million in 2003 and $26.9 million in 2002 were charged to operations as incurred.

Earnings Per Share

Basic EPS is calculated based on income available to common shareholders and the weighted-average number of shares outstanding during the reported period. Diluted EPS includes additional dilution to the Company’s earnings from common stock issuable pursuant to the exercise of stock options outstanding and effective after December 15, 2004, and the dilutive effect of contingently convertible debt instruments (see below).

In August 2003, the Company issued $100 million of 5.25% convertible senior debentures that may be converted into shares of the Company’s common stock prior to maturity, currently at a conversion price of approximately $31.00 per share, subject to adjustment in certain circumstances. The Emerging Issues Task Force (EITF) concluded in EITF Issue 04-8, “The Effect of Contingently Convertible Debt on Diluted Earnings per Share,” that contingently convertible debt (“Co-Cos”) be treated for diluted EPS purposes as if converted from debt to equity, beginning with the date the contingently convertible debt instrument is initially issued, even if the triggering events (such as stock price) have not yet occurred. The Company has implemented this consensus in its 2004 financial statements, which had the effect of lowering 2004 diluted earnings per share by $0.01 and did not have an effect on 2003 and 2002 earnings per share.

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The following table reflects the components of common shares outstanding for each of the three years ended December 31, 2004 in accordance with SFAS No. 128:

On August 6, 2004, the Company announced a 3 for 2 stock split. The shares from the stock split were distributed on September 1, 2004 to shareholders of record at the close of business on August 16, 2004. All share and per share information in this report reflects the impact of the stock split.

Employee Stock Based Compensation

The Company accounts for costs of stock-based compensation in accordance with Accounting Principles Board Opinion No. 25, “Accounting for Stock Issued to Employees,” rather than the fair-value based method in Statement of Financial Accounting Standards No. 123 (SFAS 123), “Accounting for Stock-Based Compensation.” In connection with the Armkel acquisition, the Company paid cash and issued options to purchase 97,500 shares of Company common stock at an exercise price of $22.88 per share to certain executives under Armkel’s Equity Appreciation Rights Plan (“EAR Plan”). The unvested portion of the EAR Plan options is being amortized over a two year vesting period and is recognized as expense as vesting occurs. In 2004, the amount recognized as expense for the stock options granted under the EAR Plan was approximately $0.4 million. The Company recognized compensation expense (net of tax) of approximately $0 in 2003 and $0.5 million in 2002, respectively, in accordance with APB 25. Had compensation cost been determined based on the fair values of the stock options at the date of grant in accordance with SFAS 123, the Company would have recognized additional compensation expense, net of taxes, of $4.3 million, $3.9 million and $4.5 million for 2004, 2003 and 2002, respectively, and the Company’s pro forma net income and pro forma net income per share for 2004, 2003 and 2002 would have been as follows:

Comprehensive Income

Comprehensive income consists of net income, foreign currency translation adjustments, changes in the fair value of certain derivative financial instruments designated and qualifying as cash flow hedges, and minimum pension liability adjustments, and is presented in the Consolidated Statements of Changes in Stockholders’ Equity and in note 14.

Income Taxes

The Company recognizes deferred income taxes under the liability method; accordingly, deferred income taxes are provided to reflect the future consequences of differences between the tax bases of assets and liabilities and their reported amounts in the financial statements. Management provides valuation allowances against the deferred tax asset for amounts which are not considered “more likely than not” to be realized. The Company records liabilities in income taxes payable for potential assessments in various tax jurisdictions. The liabilities relate to tax return positions, although supportable by the Company, may be challenged by the tax authorities. The Company adjusts these liabilities as a result of changes in tax legislation, interpretations of laws by Courts, rulings by tax authorities, changes in estimates and the closing of the statute of limitations. The Company’s tax rate includes the impact of the liabilities and any changes to the liabilities. Settlement of any issue with the tax authorities would require the use of cash. Favorable resolution of an issue would be recognized as a reduction to our annual tax rate. The Internal Revenue Service is currently examining the Company’s 2002 US Federal Corporation Income Tax Return.

Recent Accounting Pronouncements

In January 2004, the FASB issued FASB Staff Position (FSP) No. 106-1, “Accounting and Disclosure Requirements to the Medicare Prescription Drug, Improvement and Modernization Act of 2003” (the Act). The Act introduces a prescription drug benefit under Medicare (Medicare Part D) as well as a federal subsidy to sponsors of retiree health care benefit plans that provide a benefit that is at least actuarially equivalent to Medicare Part D. The FSP permits a sponsor of a postretirement health care plan that provides a prescription drug benefit to

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make a one-time election to defer accounting for the effects of the Act. The Company’s consolidated financial statements and notes reflect the effects of the Act on the postretirement health care plan. The effect of adopting the provisions of this FSP did not have a material effect to the Company’s consolidated financial statements.

In August 2003, the Company issued $100 million of 5.25% convertible senior debentures that may be converted into shares of the Company’s common stock prior to maturity, currently at a conversion price of approximately $31.00 per share, subject to adjustment in certain circumstances. Because of the inclusion of the contingent convertibility feature of the debentures, the Company’s diluted net income per common share does not currently give effect to the dilution from the conversion of the debentures until the Company’s share price exceeds 120% of the conversion price or until the occurrence of certain specified events. However, the Emerging Issues Task Force (EITF) concluded in EITF Issue 04-8, “The Effect of Contingently Convertible Debt on Diluted Earnings per Share,” that contingently convertible debt (“Co-Cos”) be treated for diluted EPS purposes as if converted from debt to equity, beginning with the date the contingently convertible debt instrument is initially issued, even if the triggering events (such as stock price) have not yet occurred. The effective date would be reporting periods ending on or after December 15, 2004 and prior period EPS amounts presented for comparative purposes would have to be restated. The Company has implemented this consensus in its 2004 financial statements, which had the effect of lowering 2004 diluted earnings per share by $0.01 and did not have an effect on 2003 and 2002 earnings per share.

In November 2004, the FASB issued SFAS No. 151 “Inventory Costs, an amendment for ARB. 43, Chapter 4”. This Statement requires that certain abnormal costs that were included in inventory pricing such as abnormal costs for idle facility expense, excessive spoilage, double freight, and rehandling costs be treated as current period charges. In addition, this Statement requires that allocation of fixed production overheads to the costs of conversion be based on the normal capacity of the production facilities. The provisions of this Statement shall be effective for inventory costs incurred during the fiscal years beginning after June 15, 2005. The adoption of the provisions of SFAS 151 will not have a material impact on the Company’s consolidated financial statements.

In December 2004, the FASB issued SFAS No. 123 (revised 2004), “Share-Based Payment”. SFAS No. 123R supersedes APB Opinion No. 25, which requires recognition of an expense when goods or services are provided. SFAS No. 123R requires the determination of the fair value of the share-based compensation at the grant date and the recognition of the related expense over the period in which the share-based compensation vests. SFAS No. 123R permits a prospective or two modified versions of retrospective application under which financial statements for prior periods are adjusted on a basis consistent with the pro forma disclosures required for those periods by the original SFAS No. 123. The Company is required to adopt the provisions of SFAS No. 123 R effectively July 1, 2005, at which time the Company will begin recognizing an expense for unvested share-based compensation that has been issued or will be issued after that date. Under the retroactive options, prior periods may be restated either as of the beginning of the year of adoption, January 1, 2005 for the Company, or for all periods presented. The Company has not yet finalized its decision concerning the transition option and measurement methodology it will utilize to adopt SFAS No. 123R, but estimates that the impact will not be materially different than the amounts shown in its pro forma disclosure.

The American Jobs Creation Act of 2004 (the AJCA) was enacted on October 22, 2004. The AJCA repeals an export incentive, creates a new deduction for qualified domestic manufacturing activities and includes a special one-time deduction of 85% of certain foreign earnings repatriated to the U.S.

The FASB issued FSP FAS 109-1, “Application of FASB Statement No. 109, Accounting for Income Taxes, to the Tax Deduction on Qualified Production Activities Provided by the American Jobs Creation Act of 2004” (FSP FAS 109-1) on December 21, 2004. In accordance with FSP FAS 109-1, the Company will treat the deduction for qualified domestic manufacturing activities, which is effective for the Company beginning January 1, 2005, as a reduction of the income tax provision in future years as realized.

In December 2004, the FASB issued FSP FAS 109-2, “Accounting and Disclosure Guidance for the Foreign Earnings Repatriation Provision within the American Jobs Creation Act of 2004,” allowing companies additional time to evaluate the effect of the AJCA on plans for reinvestment or repatriation of foreign earnings. The Company is in the process of evaluating the effects of the repatriation provision.

Reclassification

Certain prior year amounts have been reclassified in order to conform with the current year presentation.

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2. Fair Value of Financial Instruments and Risk Management

The following table presents the carrying amounts and estimated fair values of the Company’s financial instruments at December 31, 2004 and 2003. Financial Accounting Standards No. 107, “Disclosures About Fair Value of Financial Instruments,” defines the fair value of a financial instrument as the amount at which the instrument could be exchanged in a current transaction between willing parties.