The hockey legend endorsed Brown as the best person to become the leader of Ontario's official opposition.
"I have known Patrick Brown for a number of years now," Gretzky said in a statement. "Hard working and dedicated, Patrick is a strong Conservative. He has the passion and vision to lead Ontario."
Brown, the only leadership hopeful without a seat in the Ontario legislature, expressed his gratitude for Gretzky's words.
"I am honoured to have support from Wayne Gretzky, a Canadian icon and one of the greatest athletes of our time," Brown said in a statement.
"I am rebuilding the PC Party by reaching out to people outside our traditional voting base. I am connecting with people who share a vision of a better Ontario but who haven't felt at home with our party, and those who have never been politically active before."
Brown is running against deputy Ontario PC leader Christine Elliott, the widow of former federal finance minister Jim Flaherty, and London-area MPP Monte McNaughton.
Progressive Conservatives across the province will vote in May for the leader to replace Tim Hudak, who resigned after the Tories' fourth consecutive election loss to the Liberals last June.
Gretzky's uncle Albert ran as a Conservative in London West in the 2006 federal election,