Investor Presentation November 2023

Attractive Capital Structure Commentary . Flexible balance sheet to pursue investments in innovation and acquisitions in highly fragmented industry Montrose has $148.2 million of liquidity, including $23.2 million of cash and $125.0 million of availability under its revolving credit facility as of 9/30/23 • Weighted average interest rate at 4.4% on outstanding debt under our credit facility, incl. interest rate swaps Net leverage (1) of 1.9x as of 9/30/23 . Equity capitalization of ~$948 million (2) consisting of 1) 30.2 million shares of common stock outstanding plus 2) $182.2 million of A-2 Preferred Equity held by Oaktree (3) Total Equity Capitalization ~$948M Equity Market Capitalization Common Equity ~$766M(2) Preferred Equity $182M(3) Net Debt $145M(4) 1) The Company's leverage ratio under its credit facility includes the impact of acquisition-related contingent earnout payments that may become payable in cash. 2) As of November 3, 2023. 3) Includes Initial $175M stated value and accrued interest through July 27, 2020. 4) Net debt is a non-GAAP measure and is calculated as total debt (excluding deferred debt issuance costs) of $168.1 million less cash on hand of $23.2 million as of September 30, 2023. See the appendix to this presentation for a discussion of Net Debt. © 2023 Montrose Environmental Group, Inc. Proprietary. | 22

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