Earnings per Share ("EPS") (Tables)

9 Months Ended

Jun. 29, 2025

Earnings Per Share [Abstract]

Summary of number of weighted-average shares used to compute basic and diluted EPS

The following table presents the number of weighted-average shares used to compute basic and diluted EPS (in thousands, except per share data):

	Three Months Ended				Nine Months Ended
	June 29, 2025		June 30, 2024		June 29, 2025		June 30, 2024
Net income attributable to Tetra Tech	$	113,844	$	85,810	$	119,979	$	237,228
Weighted-average common shares outstanding – basic	263,026		267,575		265,589		267,255
Effect of dilutive stock options and unvested restricted stock	1,829		2,165		1,900		2,073
Shares issuable assuming conversion of convertible notes	—		520		624		175
Weighted-average common shares outstanding – diluted	264,855		270,260		268,113		269,503
Earnings per share attributable to Tetra Tech:
Basic	$	0.43	$	0.32	$	0.45	$	0.89
Diluted	$	0.43	$	0.32	$	0.45	$	0.88