Exhibit 99.1

GREENBROOK APPOINTS INTERIM CHIEF FINANCIAL OFFICER

October 20, 2023 – Toronto, ON – Greenbrook TMS Inc. (NASDAQ: GBNH) (“Greenbrook” or the “Company”) today announced the appointment of Mr. Peter Willett as Interim Chief Financial Officer, effective immediately.

Over the past six years, Peter has been a key player on the Greenbrook finance team, serving as its senior vice president of finance. Peter brings over 11 years of finance experience, providing a broad base of experience and specialized knowledge about the financial and accounting matters that are unique to the mental health services industry.

Peter has been instrumental in developing and implementing the financial strategies that have been successful in improving reporting functions and cost controls for Greenbrook. Peter has a proven track record of identifying effective processes and procedures to improve quality, accuracy, and efficiency in accounting and financial operations.

Peter assumes responsibilities from Erns Loubser as he pursues new opportunities. While welcoming Peter as interim CFO, the entire team at Greenbrook would like to thank Erns for his contributions as CFO and we wish him all the best in his future pursuits.

Greenbrook has retained an executive search firm and will consider Peter and other candidates as part of its process to identify the Company’s next permanent Chief Financial Officer.

About Greenbrook TMS Inc.

Operating through 133 Company-operated treatment centers, Greenbrook is a leading provider of Transcranial Magnetic Stimulation (“TMS”) and Spravato® (esketamine nasal spray), FDA-cleared, non-invasive therapies for the treatment of Major Depressive Disorder (“MDD”) and other mental health disorders, in the United States. TMS therapy provides local electromagnetic stimulation to specific brain regions known to be directly associated with mood regulation. Spravato® is offered to treat adults with treatment-resistant depression and depressive symptoms in adults with MDD with suicidal thoughts or actions. Greenbrook has provided more than 1.2 million treatments to over 38,000 patients struggling with depression.

For further information please contact:

Glen Akselrod

Investor Relations

Greenbrook TMS Inc.

Contact Information:

investorrelations@greenbrooktms.com

1-855-797-4867

Cautionary Note Regarding Forward-Looking Information

Certain information in this press release constitutes forward-looking information within the meaning of applicable securities laws in Canada and the United States, including the United States Private Securities Litigation Reform Act of 1995. In some cases, but not necessarily in all cases, forward-looking information can be identified by the use of forward-looking terminology such as “plans”, “targets”, “expects” or “does not expect”, “is expected”, “an opportunity exists”, “is positioned”, “estimates”, “intends”, “assumes”, “anticipates” or “does not anticipate” or “believes”, or variations of such words and phrases or state that certain actions, events or results “may”, “could”, “would”, “might”, “will” or “will be taken”, “occur” or “be achieved”. In addition, any statements that refer to expectations, projections or other characterizations of future events or circumstances contain forward-looking information. Statements containing forward-looking information are not historical facts but instead represent management’s expectations, estimates and projections regarding future events.

Forward-looking information is necessarily based on a number of opinions, assumptions and estimates that, while considered reasonable by the Company as of the date of this press release, are subject to known and unknown risks, uncertainties, assumptions and other factors that may cause the actual results, level of activity, performance or achievements or future events or developments to differ materially from those expressed or implied by the forward-looking statements, including, without limitation: macroeconomic factors such as inflation and recessionary conditions, substantial doubt regarding the Company’s ability to continue as a going concern due to recurring losses from operations; inability to increase cash flow and/or raise sufficient capital to support the Company’s operating activities and fund its cash obligations, repay indebtedness and satisfy the Company’s working capital needs and debt obligations; prolonged decline in the price of the Common Shares reducing the Company’s ability to raise capital; inability to satisfy debt covenants under the Company’s credit facility and the potential acceleration of indebtedness; including as a result of an unfavorable decision in respect of the litigation with Benjamin Klein; risks related to the ability to continue to negotiate amendments to the Company’s credit facility to prevent a default; risks relating to the Company’s ability to deliver and execute on the previously-announced restructuring plan (the “Restructuring Plan”) and the possible failure to complete the Restructuring Plan on terms acceptable to the Company or its suppliers (including Neuronetics, Inc.), or at all; risks relating to maintaining an active, liquid and orderly trading market for Common Shares as a result of the Company’s potential inability to regain compliance with the Nasdaq Stock Market’s listing rules; risks relating to the Company’s ability to realize expected cost-savings and other anticipated benefits from the Restructuring Plan; risks related to the Company’s negative cash flows, liquidity and its ability to secure additional financing; increases in indebtedness levels causing a reduction in financial flexibility; inability to achieve or sustain profitability in the future; inability to secure additional financing to fund losses from operations and satisfy the Company’s debt obligations; risks relating to strategic alternatives, including restructuring or refinancing of the Company’s debt, seeking additional debt or equity capital, reducing or delaying the Company’s business activities and strategic initiatives, or selling assets, other strategic transactions and/or other measures, including obtaining bankruptcy protection, and the terms, value and timing of any transaction resulting from that process; claims made by or against the Company, which may be resolved unfavorably to us; risks relating to the Company’s dependence on Neuronetics, Inc. as its exclusive supplier of TMS devices. Additional risks and uncertainties are discussed in the Company’s materials filed with the Canadian securities regulatory authorities and the United States Securities and Exchange Commission from time to time, available at www.sedarplus.com and www.sec.gov, respectively. These factors are not intended to represent a complete list of the factors that could affect the Company; however, these factors should be considered carefully. There can be no assurance that such estimates and assumptions will prove to be correct. The forward-looking statements contained in this press release are made as of the date of this press release, and the Company expressly disclaims any obligation to update or alter statements containing any forward-looking information, or the factors or assumptions underlying them, whether as a result of new information, future events or otherwise, except as required by law.