McCarthy ran unsuccessfully in
2011 and
2014 to become the Member of Provincial Parliament for the riding of
Ajax-Pickering and lost in the riding of
Whitby in the
2019 federal election. In 2021, McCarthy was nominated to be the
Progressive Conservative Party of Ontario candidate for Durham. He then went on to win a seat in the riding of
Durham the
2022 Ontario general election, winning by over 10,000 votes. He has since been appointed a parliamentary assistant to the
president of the Treasury Board, deputy government whip and as a member of the Standing Committee on Public Accounts. McCarthy briefly served as the
Associate Minister of Transportation from September 4 to September 22, 2023 and was later shuffled to be the Minister of Public and Business Service Delivery on September 22, 2023 after the resignation of
Kaleed Rasheed. As Minister of Public and Business Service Delivery and Procurement, McCarthy introduced four pieces of legislation that were passed unanimously by the Legislative Assembly of Ontario within an 11-month period: 1) Bill 142,
The Better for Consumers, Better for Businesses Act, 2023 , received Royal Assent on December 6, 2023. This act repealed the
Consumer Protection Act, 2002, and replaced it with the
Consumer Protection Act, 2023. The new legislation modernizes consumer protection laws, addressing unfair business practices, and enhances transparency in consumer transactions. 2) Bill 153,
The Building Infrastructure Safely Act, 2024, received Royal Assent in early 2024. This act amends the
Ontario Underground Infrastructure Act, 2012, and introduces new rules for liability, fee collection and locate requests, aiming to improve safety and efficiency in infrastructure projects. 3) Bill 194,
The Strengthening Cyber Security and Building Trust in the Public Sector Act, 2024, received Royal Assent in November 2024. This act enhances digital security and trust within Ontario's public sector. It includes provisions for cybersecurity, artificial intelligence governance, and stronger privacy protections for children and youth. 4) Bill 200,
The Homeowner Protection Act, 2024, received Royal Assent on June 6, 2024. This act aims to protect homeowners from predatory lending schemes by banning the registration of Notices of Security Interest (NOSI) on land titles. It also introduces a cooling-off period for buyers of new freehold homes. While serving as the Minister of Public and Business Service Delivery and Procurement, McCarthy acted as Minister of Environment, Conservation and Parks between September 2024 and March 2025. He assumed these duties when Minister, Andrea Khanjin, went on parental leave. On March 19, 2025, McCarthy was sworn in as Minister of the Environment, Conservation and Parks. He won re-election in the
2025 Ontario general election. During the 2025 Ontario general election McCarthy reportedly told a potential voter he was canvassing for that a video explaining Doug Ford wanting to open the Greenbelt for development was fake news and may have been created by artificial intelligence. McCarthy served as Ontario’s Minister of the Environment, Conservation and Parks during a period in which the Ford government emphasized the streamlining of environmental approvals and regulatory requirements, particularly for mining development in the
Ring of Fire region. These initiatives were introduced amid the threat of tariffs on Canada during the second
Trump Administration. On December 18, 2025, he co-signed the
Cooperation Agreement Between Ontario and Canada on Environmental and Impact Assessments joining Premier Doug Ford in Ottawa alongside Prime Minister
Mark Carney for a federal–provincial agreement adopting a “One Project, One Process” framework, intended to align and accelerate approval processes for major mining and resource development projects, including those in the Ring of Fire. McCarthy was appointed Acting
Minister of Infrastructure on October 9, 2025 while continuing to serve as Ontario's Minister of Environment Conservation and Parks. This was necessitated by the absence of Minister
Kinga Surma while on parental leave. == Personal life ==