#1 The reporting person's previous Forms 4 erroneously overstated the number of shares of Common Stock beneficially owned. The amount in Column 5 of Table I has been corrected in this Form 4.

#1 On March 1, 2021, the reporting person was granted an award of performance stock units (PSUs), which vest in the form of common stock based upon the Issuer's performance against certain strategic objective goals. On February 27, 2024, the Compensation Committee of the Issuer's Board of Directors determined that the strategic objective goals had been met, resulting in the vesting of these shares.

#2 Includes 519 shares of common stock automatically purchased on behalf of the reporting person pursuant to the terms of the Parsons Employee Stock Purchase Plan.

#1 On March 1, 2021, the reporting person was granted an award of performance stock units (PSUs), which vest in the form of common stock based upon the Issuer's performance against certain strategic objective goals. On February 27, 2024, the Compensation Committee of the Issuer's Board of Directors determined that the strategic objective goals had been met, resulting in the vesting of these shares.

#2 Includes 519 shares of common stock automatically purchased on behalf of the reporting person pursuant to the terms of the Parsons Employee Stock Purchase Plan.

#1 Represents an award of restricted stock units ("RSUs"). Each RSU represents a contingent right to receive one share of common stock. The RSUs will vest in four equal annual installments beginning on December 18, 2024 and have no expiration date.