Exhibit 99.1 Montrose Environmental Group Reports Record Third Quarter and First Nine Months 2024 Results, Reaffirms Guidance, and Updates Strategic Capital Allocation Priorities Third Quarter 2024 Highlights (comparisons to third quarter 2023) • Highest-ever total revenue of $178.7 million, an increase of $10.8 million, or 6.4% • Net loss of $10.6 million, or $0.39 net loss per diluted share attributable to common stockholders (LPS), and Adjusted Net Income 1 of $19.1 million, or $0.41 Diluted Adjusted Net ...