Dan Batrack, Chairman & CEOSteve Burdick, Executive VP & CFO

EARNINGS CALLQ1-20January 30, 2020

WATER ENVIRONMENT SUSTAINABLE INFRASTRUCTURE

Certain statements contained in this presentation are forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. These statements involve risks and uncertainties, such as those related to fluctuations in the Company’s quarterly operating results and stock price, and the other risks detailed from time to time in the Company’s SEC reports.

To supplement the financial results presented in accordance with generally accepted accounting principles in the United States (“GAAP”), we present certain non-GAAP financial measures within the meaning of Regulation G under the Securities Exchange Act of1934, as amended. We provide these non-GAAP financial measures because we believe they provide a valuable perspective on our financial results. However, non-GAAP measures have limitations as analytical tools and should not be considered in isolation and are not in accordance with, or a substitute for, GAAP measures. In addition, other companies may define non-GAAP measures differently which limits the ability of investors to compare non-GAAP measures of Tetra Tech to those used by our peer companies. A reconciliation of these non-GAAP financial measures to the most directly comparable GAAP financial measures is included in the Appendix to this presentation.

Forward Looking Statements & Non-GAAP Financial Measures

2

Note: Financial measures (non-GAAP) and Y/Y presented on adjusted basis. Refer to appendix for reconciliation summary.

Net Revenue

$553M$614M

+11%

Q1-19 Q1-20

$0.70

$0.84

+20%

Q1-19 Q1-20

$2.79B$3.17B

+13%

Q1-19 Q1-20

EPS Backlog

Q1-20 Results

3

Net Revenue by Customer (Q1-20)

U.S. Federal 28% U.S. Commercial 24% U.S. State & Local 14%International 34%

UK environmental

Renewable energy

4

+25% +12% -7%

U.S renewable energy

Environmental remediation

Water and environmental programs

Disaster Response

Water infrastructure (+10% Y/Y)

+5%

Net Revenue by Segment (Q1-20) ($ in millions)

GSG CIG

+14%

$250

$284$303

$330

+9%

Broad-based water and environmental programs

Disaster response

North America renewable energy

UK environmental consulting

Q1-19 Q1-20Q1-19 Q1-20

5

Backlog (Q1-20)

2200

2300

2400

2500

2600

2700

2800

2900

3000

3100

3200

Q1-18 Q2-18 Q3-18 Q4-18 Q1-19 Q2-19 Q3-19 Q4-19 Q1-20

$2.43B

Record High

Funded and

Authorized Work

Significant AwardsContract Ceiling

Funded Value

Various Commercial ― $344M

Int’l Dev Task Orders ― $181M

USACE Transatlantic Middle East District A&E Contract

$45M ―

U.S. Army Task Orders ― $41M

U.S. EPA Ecological & Human Health contract

$21M ―

U.S. EPA Task Orders ― $12M

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$3.17B

Financial Overview (GAAP)

Net Revenue ($ in millions)

+11% Y/Y

Q1-19 Q1-20

Revenue ($ in millions)

+11% Y/Y

Q1-19 Q1-20

$717$798

7

Operating Income ($ in millions)

Q1-19 Q1-20

+14% Y/Y

$63

Diluted EPS

Q1-19 Q1-20

$0.75 +13% Y/Y

Adj. EPS

+20% Y/Y

$0.85

$56

$553$614

Cash Flow Overview

Cash Flow from Operations ($ in millions)

-18% Y/Y

Q1-20Q1-19

$(15)$(18)

Net Debt ($ in millions)

Net debt/EBITDA: 0.8x

$194$224

Q1-20Q1-19

DSO

10-day improvement

Y/Y

Q1-20Q1-19

8373

8

Capital AllocationQ1-20

• Add’l $200M buyback approved

• $304M buyback capacity

• $8.2M in dividends

• Geographical

• Technical

• Clients

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• Net Debt/EBITDA: 0.8x

Return to Shareholders

CurrentLeverage

Cash Flowfrom

Operations

Acquisitions

Fiscal 2020 Outlook

Leadingwith

Science®

U.S. Federal

Drivers:

▪ Increase in U.S. Federal budget

U.S. State and Local

Drivers:

▪ Municipal water infrastructure

▪ Disaster recovery

International

Drivers:

▪ Infrastructure and environmental programs

U.S. Commercial

Drivers:

▪ Environmental services

▪ Sustainable buildings5% to 10%

10

10% to 15%*

3% to 8%

7% to 12%

* Excludes disaster response

U.S. Federal: Increased funding and visibility

+16% Y/Y

11

Defense

+16% Y/Y

Civilian Agencies International Development

FY20 Budget $738B; +$22B Y/Y $607B; +$53B Y/Y $55B; +467M Y/Y

• $1.4 trillion fiscal 2020 spending bills approved in December 2019 provide more visibility

• Leverage Tt’s $18B in U.S. Federal contract capacity

Commercial Mixed Use

+16% Y/Y

Net Zero School

+16% Y/Y

Sustainable High-Performance Buildings

International Towers Sydney

+16% Y/Y

School building generates surplus energy - 140,000 kWh per year

• Demand for sustainable buildings that:

− Generate more power than they use

− Capture and recycle water

− Minimize waste and promote recycling

• Grow $250M practice to $500M annual revenue

Harbor water cooling system - 100M liters of potable water saved per year

Recycles 54,000 gallons of water daily

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Guidance

Net Revenue Adjusted Diluted EPS

Q2-20 $580M - $630M $0.73 - $0.78

FY-20 $2.4B - $2.6B $3.40 - $3.55

Assumptions FY-20

• Includes intangible amortization of $10 million or $0.14 per share

• 23% effective tax rate for remainder of FY-20

• 55.5 million average diluted shares

• Excludes contributions from future acquisitions

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• Record first quarter start to fiscal 2020

• Broad-based demand for high-end consulting and engineering services

• Strong orders drove backlog to all-time high

Summary

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Questions & Answers

15

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APPENDIX

WATER ENVIRONMENT SUSTAINABLE INFRASTRUCTURE

Reconciliation Summary($ in millions, except EPS)

Revenue Net Revenue Operating Income EPS

GAAP $798 $614 $63 $0.85

Non-core Equipment Disposition

― ― (1) (0.01)

Adjusted $798 $614 $62 $0.84

Revenue Net Revenue Operating Income EPS

GAAP $717 $553 $56 $0.75

Revaluation of Deferred Tax Liabilities

― ― ― (0.05)

Adjusted $717 $553 $56 $0.70

Q1-19

17

Q1-20