(Mark One)ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 ☒ 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 if the Registrant is not required to file reports pursuant to Section 13 or 15(d) of the Act. Yes☐No☒ 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 1934during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filingrequirements for the past 90 days.Yes☒No☐ Indicate by check mark whether the Registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 ofRegulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the Registrant was required to submit suchfiles).Yes☒No☐ Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company, or anemerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growthcompany” in Rule 12b-2 of the Exchange Act. Large accelerated filer☒Non-accelerated filer☐Emerging growth company☐ Smaller reporting company If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any newor revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.☐ Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internalcontrol over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that preparedor issued its audit report.☒ If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in thefiling reflect the correction of an error to previously issued financial statements.☐ Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensationreceived by any of the registrant’s executive officers during the relevant recovery period pursuant to §240.10D-1(b).☐ Indicate by check mark whether the Registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes☐No☒ The number of shares of Registrant’s Common Stock outstanding as of February 11, 2025 was106,777,126 DOCUMENTS INCORPORATED BY REFERENCE Portions of Parsons’ 2025 Proxy Statement are incorporated by reference into Part III of this Annual Report on Form 10-K. Table of Contents PART I Item 1.BusinessItem 1A.Risk FactorsItem 1B.Unresolved Staff CommentsItem 1C.CybersecurityItem 2.PropertiesItem 3.Legal ProceedingsItem 4.Mine Safety Disclosures PART II Item 5.Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of EquitySecurities54Item 6.Reserved56Item 7.Management’s Discussion and Analysis of Financial Condition and Results of Operations57Item 7A.Quantitative and Qualitative Disclosures About Market Risk82Item 8.Financial Statements and Supplementary Data82Item 9.Changes in and Disagreements With Accountants on Accounting and Financial Disclosure82Item 9A.Controls and Procedures82Item 9B.Other Information83Item 9C.Disclosure Regarding Foreign Jurisdictions that Prevent Inspections83 PART III Item 10.Directors, Executive Officers and Corporate Governance84Item 11.Executive Compensation84Item 12.Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters84Item 13.Certain Relationships and Related Transactions, and Director Independence84Item 14.Principal Accounting Fees and Services84 PART IV Item 15.Exhibits, Financial Statement Schedules85Item 16Form 10-K Summary85Exhibit Index86 Signatures90Index to Consolidated Financial Statements and Report of Independent Registered Public AccountingFirmF-1 SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS This annual report on Form 10-K contains forward-looking statements within the meaning of the federal securitieslaws, which statements involve substantial risks and uncertainties. Forward-looking statements generally relate to futureevents or our future financial or operating performance. In some cases, you can identify forward-looking statementsbecause they contain words such as “may”, “will”, “should”, “expects”, “plans”, “anticipates”, “could”, “intends”, “target”,“projects”, “contemplates”, “believes”, “estimates”, “predicts”, “potential” or “continue” or the negative of these words orother similar terms or expressions that concern our expectations, strategy