Investor Presentation November 2023

Our Revenue is Resilient Due to Regulatory Underpinning and Diverse Customer Base • Revenue retention is strong and consistent: clients generating 95%+ revenue in FY2021 repeated in FY2022, consistent with prior years Approximately 5,600 clients in . 2022; largest client represents ~14% of revenue 89%/11% revenue split between private and public clients Revenue End Market Mix 2022 8.3% 8.5% 3.2% 0.6% 3.9% ■Manufacturing Oil & Gas 8.2% 22.9% 9.5% 11.3% 10.1% Fed/State/Local Gov Media Utilities Renewable Energy Consumer Products 13.2% Technical Services Chemicals Other ■Aerospace © 2023 Montrose Environmental Group, Inc. Proprietary. | 8

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