Quarterly Financial Information – Unaudited (Tables)

12 Months Ended

Sep. 29, 2024

Quarterly Financial Information Disclosure [Abstract]

Schedule of unaudited quarterly data

	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
Fiscal Year 2024
Revenue	$	1,228,267	$	1,251,616	$	1,344,323	$	1,374,473
Income from operations	111,081		117,683		128,630		143,343
Net income attributable to Tetra Tech	74,972		76,446		85,810		96,154
Earnings per share attributable to Tetra Tech:
Basic	$	0.28	$	0.29	$	0.32	$	0.36
Diluted	$	0.28	$	0.28	$	0.32	$	0.35
Weighted-average common shares outstanding:
Basic	266,585		267,420		267,575		267,687
Diluted	268,690		269,375		270,260		271,656
Fiscal Year 2023
Revenue	$	894,766	$	1,158,226	$	1,208,947	$	1,260,611
Income from operations	92,050		61,011		97,675		107,377
Net income attributable to Tetra Tech	116,706		42,830		60,235		53,649
Earnings per share attributable to Tetra Tech:
Basic	$	0.44	$	0.16	$	0.23	$	0.20
Diluted	$	0.44	$	0.16	$	0.22	$	0.20
Weighted-average common shares outstanding:
Basic	265,345		266,135		266,155		266,235
Diluted	267,645		268,135		268,265		268,510