Investor Presentation November 2023

We Have Consistently Created Value for Our Shareholders Organic Earnings Growth (+) • Average annual organic revenue growth (1) of ~16% since Montrose's IPO in 2020 ⚫ Revenue synergies catalyze cross-selling (2) success by creating environmental value for clients, accounting for 35% of revenues in 2022 • Positioned to continue strong organic growth given industry tailwinds, differentiated IP and software • Successful investments in R&D have furthered organic growth opportunities and increased barriers to entry Strategically Additive Acquisitions (+) . . Acquisitions represent a core part of growth strategy within highly fragmented environmental industry - Environmental services industry comprised of thousands of firms Strategic acquisitions purchased at an average of mid-to-high single-digit multiples to-date can generate significant shareholder value over time • Positioned to acquire an expected $10-15 million of annualized EBITDA per year at attractive values 1) Excludes discontinued service lines, which generated revenues of $17.1 million in 2020, $12.1 million in 2021, and $3.6 million in 2022. See the appendix for a discussion of how we calculate organic growth. 2) Cross-selling activity defined as the percentage of total revenue from customers purchasing two or more Montrose services (other than those provided by CTEH) within the same fiscal year. © 2023 Montrose Environmental Group, Inc. Proprietary. | 9

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