Sarah Thomson is set to announce she's joining the Toronto mayoral race on Thursday.

Thomson, a transit advocate and the publisher of Women's Post, will file her papers at 8:30 a.m. Thursday at city hall.

Thomson will be joining Olivia Chow, former Ontario Progressive Conservative Party leader John Tory, former Toronto Transit Commission chair Karen Stintz and former city councillor David Soknacki in the race.

This is the second time Thomson is running to be the mayor of Toronto. She withdrew from the 2010 municipal election.