Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2024	Jul. 02, 2023	Jun. 30, 2024	Jul. 02, 2023
Revenue	$ 1,344,323	$ 1,208,947	$ 3,824,205	$ 3,261,938
Gross profit	223,172	188,846	621,165	512,937
Selling, general and administrative expenses	(94,042)	(89,064)	(263,293)	(227,912)
Acquisition and integration expenses	0	(2,107)	0	(25,812)
Contingent consideration – fair value adjustments	(500)	0	(477)	(8,477)
Income from operations	128,630	97,675	357,395	250,736
Interest expense, net	(9,912)	(14,869)	(29,374)	(33,563)
Other non-operating income	0	0	0	89,402
Income before income tax expense	118,718	82,806	328,021	306,575
Income tax expense	(32,894)	(22,568)	(90,758)	(86,781)
Net income	85,824	60,238	237,263	219,794
Net income attributable to noncontrolling interests	(14)	(3)	(35)	(23)
Net income attributable to Tetra Tech, basic	85,810	60,235	237,228	219,771
Net income attributable to Tetra Tech, diluted	$ 85,810	$ 60,235	$ 237,228	$ 219,771
Earnings per share attributable to Tetra Tech:
Basic (in dollars per share)	$ 1.60	$ 1.13	$ 4.44	$ 4.13
Diluted (in dollars per share)	$ 1.59	$ 1.12	$ 4.40	$ 4.10
Weighted-average common shares outstanding:
Basic (in shares)	53,515	53,231	53,451	53,188
Diluted (in shares)	54,052	53,653	53,901	53,615
Subcontractor costs
Cost of revenue	$ (234,742)	$ (221,387)	$ (646,828)	$ (568,252)
Other costs of revenue
Cost of revenue	$ (886,409)	$ (798,714)	$ (2,556,212)	$ (2,180,749)