Trevor was first elected to Antrim Borough Council in 2005 to serve the people of Antrim North West.
He was first elected to represent the people of South Antrim at the Assembly in 2007 and was re-elected in 2011. He was Deputy Chair of the Procedures Committee prior to his appointment as Chair of the Regional Development Committee. He has also served as Chief Whip of the DUP Assembly Group.
Following the election of Paul Girvan as MP for South Antrim Trevor was co-opted to the Northern Ireland Assembly in 2017.
Since 2020, Trevor has been a member of the Executive Office Committee. He is also on the All-Party groups for Cancer, Terminal Illness and Modern Slavery.