Exhibit 99.1

MONTROSE ENVIRONMENTAL GROUP ANNOUNCES FIRST QUARTER 2024 RESULTS

- Record First Quarter Revenue of $155.3 Million, up 18% Year-Over-Year -

- Net Loss of $13.4 million; Basic and Diluted Net Loss Per Share of $0.53 -

- Record First Quarter Consolidated Adjusted EBITDA1 of $16.9 Million -

- Executed Three Highly Accretive Acquisitions and Expanded Patent Portfolio -

- Reiterates Recently Raised 2024 Revenue and Consolidated Adjusted EBITDA1 Guidance -

Little Rock, Arkansas (May 7, 2024) – Montrose Environmental Group, Inc. (the “Company,” “Montrose” or “MEG”) (NYSE: MEG) today announced results for the first quarter ended March 31, 2024.

Montrose Chief Executive Officer and Director, Vijay Manthripragada, commented, “The momentum in our business continues as we start 2024 with solid first quarter results. Our organic growth and outlook remain very strong, and our cadence of strategic acquisitions has increased. We saw strength across our business lines given secular and regulatory tailwinds, particularly in our advisory and lab services, and we expect momentum to build over the year within our remediation services. This broad strength across our services resulted in record first quarter revenues and Consolidated Adjusted EBITDA1.”

Mr. Manthripragada continued, “With the US EPA’s establishment of maximum contaminant levels for several PFAS in April, coupled with new regulations and increased enforcement of GHG emissions and other air pollutants in Q1, we foresee a steady acceleration in customer activity across all elements of our business. As a result, we remain incredibly optimistic about Montrose’s long-term growth potential, and we are confident in our ability to create significant value for our shareholders and achieve our recently increased 2024 guidance.”

First Quarter 2024 Results

Total revenue in the first quarter of 2024 was $155.3 million compared to $131.4 million in the prior year quarter, an increase of 18.2%. The increase in revenues was primarily due to strong organic revenue growth in our Assessment, Permitting and Response and Measurement and Analysis segments, and the contributions of acquisitions, partially offset by lower environmental emergency response service revenues, the exiting of the Discontinued Specialty Lab in December 2023, and the shift away from lower margin revenue in our biogas business.

Net loss was $13.4 million, or a loss of $0.53 per share basic and diluted, in the first quarter of 2024 compared to a net loss of $14.7 million, or a loss of $0.63 per share basic and diluted, in the prior year quarter. The year-over-year reduction in net loss and net loss per share was primarily attributable to a net gain from fair value adjustments related to our interest rate swaps, compared to a net loss from fair value adjustments related to our Series A-2 preferred stock conversion option and interest rate swaps in the prior year, as well as lower income tax expense in the current year, partially offset by higher interest expense in the current year.

Adjusted Net Income1 was $8.4 million, and Diluted Adjusted Net Income per Share1 was $0.16, in the first quarter of 2024 compared to Adjusted Net Income1 of $10.4 million, and Diluted Adjusted Net Income per Share1 of $0.17 in the prior year quarter. Both Adjusted Net Income and Diluted Adjusted Net Income per Share were lower as a result of higher interest and depreciation in the current period versus the prior year, partially offset by lower income tax expense. Current year Diluted Adjusted Net Income per Share also benefitted from lower dividends on our Series

A-2 preferred stock following the partial redemption. Diluted Adjusted Net Income per Share1 is calculated as Adjusted Net Income1 attributable to stockholders divided by fully diluted shares.

First quarter 2024 Consolidated Adjusted EBITDA1 was $16.9 million, compared to $16.6 million in the prior year quarter. The increase in Consolidated Adjusted EBITDA1, was due to higher revenues. Consolidated Adjusted EBITDA1 as a percentage of revenues decreased primarily due to the acquisition of Matrix in June 2023, which typically experiences low or negative margins in the first quarter due to seasonality.

Operating Cash Flow, Liquidity and Capital Resources

Cash used in operating activities for the first quarter ended March 31, 2024 was $22.0 million compared to cash provided by operating activities of $3.0 million in the prior year quarter. Lower cash flow from operations was driven primarily by the timing of temporary working capital spend in the current quarter compared to the prior year. Cash flow from operating activities is expected to improve over the course of the year and expectations for full-year cash generation are consistent with prior years.

In January 2024, Montrose voluntarily redeemed $60.0 million of the outstanding Convertible and Redeemable Series A-2 Preferred Stock with cash. Following this redemption, the principal balance of the Series A-2 Preferred Stock outstanding was reduced to $122.2 million and remains classified as mezzanine equity.

In February 2024, the Company amended its Senior Secured Credit Agreement, to provide for an additional $100.0 million in credit availability, comprised of an additional $50.0 million term loan and $50.0 million revolving credit facility. As of March 31, 2024, we had total debt, before debt issuance costs, of $297.7 million.

In April 2024, Montrose completed a public offering of 3,450,000 shares of its common stock, raising approximately $122.4 million in proceeds, net of underwriting discounts and commissions. The proceeds from the offering have been and will be used for general corporate purposes and continued acceleration of strategic growth initiatives, including, but not limited to, acquisitions or business expansion, commercialization of intellectual property given expanded environmental regulations, research and development, software development, capital expenditures, working capital and the repayment of debt.

Pro forma for the offering, Montrose had $218.8 million of liquidity, including $43.8 million of cash and $175 million of availability on its revolving credit facility, as of March 31, 2024, and a leverage ratio of 2.1 times.

Acquisitions

In January 2024, Montrose acquired Epic Environmental, a leading environmental consultancy in Australia. Headquartered in Brisbane, Epic Environmental is part of the Company’s Remediation and Reuse segment.

In February 2024, Montrose acquired Two Dot Environmental Consulting, a leading environmental consultancy focused on energy and renewable energy clients in the Rocky Mountain region of the U.S. Two Dot is part of the Company’s Remediation and Reuse segment.

In April 2024, Montrose acquired Engineering & Technical Associates., a leader in Process Safety Management. ETA is part of the Company’s Assessment, Permitting & Response segment.

Full Year 2024 Outlook

The Company reiterates its full year 2024 Revenue and Consolidated Adjusted EBITDA1 outlook provided on April 2, 2024. The company expects Revenue to be in the range of $690 million to $740 million. Consolidated Adjusted EBITDA1 is expected to be in the range of $95 million to $100 million for the full year 2024. The midpoints of the ranges incorporate an expectation of low double digit organic revenue growth and continued year-on-year Consolidated Adjusted EBITDA1 margin expansion.

Our Revenue and Consolidated Adjusted EBITDA1 outlook does not include any benefit from future acquisitions.

Webcast and Conference Call

The Company will host a webcast and conference call on Wednesday, May 8, 2024 at 8:30 a.m. Eastern time to discuss first quarter financial results. Their prepared remarks will be followed by a question and answer session. A live webcast of the conference call will be available in the Investors section of the Montrose website at www.montrose-env.com. The conference call will also be accessible by dialing 1-888-886-7786 (Domestic) and 1-416-764-8658 (International). For those who are unable to listen to the live broadcast, an audio replay of the conference call will be available on the Montrose website for 30 days.

About Montrose

Montrose is a leading environmental solutions company focused on supporting commercial and government organizations as they deal with the challenges of today, and prepare for what’s coming tomorrow. With ~3200 employees across 100+ locations worldwide, Montrose combines deep local knowledge with an integrated approach to design, engineering, and operations, enabling Montrose to respond effectively and efficiently to the unique requirements of each project. From comprehensive air measurement and laboratory services to regulatory compliance, emergency response, permitting, engineering, and remediation, Montrose delivers innovative and practical solutions that keep its clients on top of their immediate needs – and well ahead of the strategic curve. For more information, visit www.montrose-env.com.

Forward‐Looking Statements

This press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. Forward-looking statements may be identified by the use of words such as “intend,” “expect”, and “may”, and other similar expressions that predict or indicate future events or that are not statements of historical matters. Forward-looking statements are based on current information available at the time the statements are made and on management’s reasonable belief or expectations with respect to future events, and are subject to risks and uncertainties, many of which are beyond the Company’s control, that could cause actual performance or results to differ materially from the belief or expectations expressed in or suggested by the forward-looking statements. Additional factors or events that could cause actual results to differ may also emerge from time to time, and it is not possible for the Company to predict all of them. Forward-looking statements speak only as of the date on which they are made, and the Company undertakes no obligation to update any forward-looking statement to reflect future events, developments or otherwise, except as may be required by applicable law. Investors are referred to the Company’s filings with the Securities and Exchange Commission, including its Annual Report on Form 10-K for the year ended December 31, 2023, for additional information regarding the risks and uncertainties that may cause actual results to differ materially from those expressed in any forward-looking statement.

Contact Information:

Investor Relations:

Rodny Nacier

(949) 988-3383

ir@montrose-env.com

Media Relations:

Sarah Kaiser

(225) 955-1702

pr@montrose-env.com

MONTROSE ENVIRONMENTAL GROUP, INC.

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND
COMPREHENSIVE LOSS

(In thousands, except per share data)

MONTROSE ENVIRONMENTAL GROUP, INC.

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF FINANCIAL POSITION

(In thousands, except share data)

MONTROSE ENVIRONMENTAL GROUP, INC.

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

(In thousands)

MONTROSE ENVIRONMENTAL GROUP, INC.

SEGMENT REVENUES AND ADJUSTED EBITDA

(In thousands)

(Unaudited)

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Non-GAAP Financial Information

In addition to our results under GAAP, in this release we also present certain other supplemental financial measures of financial performance that are not required by, or presented in accordance with, GAAP, including, Consolidated Adjusted EBITDA, Adjusted Net Income and Basic and Diluted Adjusted Net Income per Share. We calculate Consolidated Adjusted EBITDA as net income (loss) before interest expense, income tax expense (benefit) and depreciation and amortization, adjusted for the impact of certain other items, including stock-based compensation expense and acquisition-related costs, as set forth in greater detail in the table below. We calculate Adjusted Net Income as net income (loss) before amortization of intangible assets, stock-based compensation expense, fair value changes to financial instruments and contingent earnouts, discontinued specialty lab, and other gain or losses, as set forth in greater detail in the table below. Basic and Diluted Adjusted Net Income per Share represents Adjusted Net Income attributable to stockholders divided by the fully diluted number of shares of common stock outstanding during the applicable period.

Consolidated Adjusted EBITDA is one of the primary metrics used by management to evaluate our financial performance and compare it to that of our peers, evaluate the effectiveness of our business strategies, make budgeting and capital allocation decisions and in connection with our executive incentive compensation. Adjusted Net Income and Basic and Diluted Adjusted Net Income per Share are useful metrics to evaluate ongoing business performance after interest and tax. These measures are also frequently used by analysts, investors and other interested parties to evaluate companies in our industry. Further, we believe they are helpful in highlighting trends in our operating results because they allow for more consistent comparisons of financial performance between periods by excluding gains and losses that are non-operational in nature or outside the control of management, and, in the case of Consolidated Adjusted EBITDA, by excluding items that may differ significantly depending on long-term strategic decisions regarding capital structure, the tax jurisdictions in which we operate and capital investments.

These non-GAAP measures do, however, have certain limitations and should not be considered as an alternative to net income (loss), earnings (loss) per share or any other performance measure derived in accordance with GAAP. Our presentation of Consolidated Adjusted EBITDA, Adjusted Net Income and Basic and Diluted Adjusted Net Income per Share should not be construed as an inference that our future results will be unaffected by unusual or non-recurring items for which we may make adjustments. In addition, Consolidated Adjusted EBITDA, Adjusted Net Income and Basic and Diluted Adjusted Net Income per Share may not be comparable to similarly titled measures used by other companies in our industry or across different industries, and other companies may not present these or similar measures. Management compensates for these limitations by using these measures as supplemental financial metrics and in conjunction with our results prepared in accordance with GAAP. We encourage investors and others to review our financial information in its entirety, not to rely on any single measure and to view Consolidated Adjusted EBITDA, Adjusted Net Income and Basic and Diluted Adjusted Net Income per Share in conjunction with the related GAAP measures.

Additionally, we have provided estimates regarding Consolidated Adjusted EBITDA for 2024. These projections account for estimates of revenue, operating margins and corporate and other costs. However, we cannot reconcile our projection of Consolidated Adjusted EBITDA to net income (loss), the most directly comparable GAAP measure, without unreasonable efforts because of the unpredictable or unknown nature of certain significant items excluded from Consolidated Adjusted EBITDA and the resulting difficulty in quantifying the amounts thereof that are necessary to estimate net income (loss). Specifically, we are unable to estimate for the future impact of certain items, including income tax (expense) benefit, stock-based compensation expense, fair value changes and the accounting for the issuance of the Series A-2 preferred stock. We expect the variability of these items could have a significant impact on our reported GAAP financial results.

In this release we also reference our organic growth. We define organic growth as the change in revenues excluding revenues from i) our environmental emergency response business, ii) acquisitions for the first twelve months following the date of acquisition, and iii) businesses held for sale, disposed of or discontinued. As a result of the growth in CTEH non-emergency response work, which is similar to services provided in our advisory businesses, we are including CTEH revenues from non-emergency response work in organic growth. This change did not impact previously reported organic growth. Management uses organic growth as one of the means by which it assesses our results of operations. Organic growth is not, however, a measure of revenue growth calculated in accordance with U.S. generally accepted accounting principles, or GAAP, and should be considered in conjunction with revenue growth calculated in accordance with GAAP. We have grown organically over the long term and expect to continue to do so.

Montrose Environmental Group, Inc.

Reconciliation of Net Loss to Adjusted Net Income

(In thousands)

(Unaudited)

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Montrose Environmental Group, Inc.

Reconciliation of Net Loss to Consolidated Adjusted EBITDA

(In thousands)

(Unaudited)

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