The by-election was triggered by the resignation of Terry Mulder on 3 September 2015.

Former Premier of Victoria, Denis Napthine, resigned his seat representing the adjacent district of South-West Coast on the same day as Mulder.

The Labor government did not contest the by-elections in the safe Liberal seats of Polwarth and South-West Coast.

Candidates and parties which suggested preferences are shown in each column of the table below.

The Australian Sex Party ran an open card at this by-election.