As a Member of the Legislative Assembly of British Columbia, Mary Polak has represented the constituents of Langley since 2005. Shortly after being reelected to the B.C. legislature in 2013, she was appointed Minister of Environment. Prior to this position, Polak held a variety of the roles within the legislature, having served as the Minister of Healthy Living and Sport and, most recently, Minister of Transportation and Infrastructure. In her current role, she is actively involved as the vice-chair of the Environment and Land Use Committee, and is a member of both the Cabinet Working Group on Liquefied Natural Gas and the Priorities and Planning Committee.

Before being elected to the Legislative Assembly, Polak served as a trustee and former chair of the Surrey School Board in Surrey, British Columbia.