Derek Mombourquette was first elected to the Nova Scotia House of Assembly as MLA for Sydney-Whitney Pier in a by-election in 2015, re-elected in 2017 and re-elected for Sydney-Membertou in 2021.

Mr. Mombourquette is currently the Opposition House Leader.

He has served as the Minister of Education and Early Childhood Development, Minister of Municipal Affairs, Minister of Energy and Mines and Minister of Lands and Forestry.

Prior to his election in 2015 he served on the Cape Breton Regional Municipality Council. As a Councillor he was Chair of the CBRM Police Commission and served on the NS Association of Police Boards. In addition, he was the VP of the Canadian Association of Police Governance. He has also held the role of Chair for the CBRM Heritage Advisory Committee.

Outside of politics, he was the coordinator of entrepreneurship support initiatives for Cape Breton University and the Nova Scotia Community College. He has also held the position of project coordinator in several industries within the private sector including tourism, industrial supply, and post-secondary education.

He is a member of the Assembly Matters and Internal Affairs Committees. He is also a member of the House of Assembly Management Commission.