Christopher Peloso, 39, was last seen in Toronto's Davenport Road and Bathurst Street area at 4 p.m. on Monday afternoon. He was going for a walk near his home.
Peloso is a 5'8" white male, who weighs about 150 pounds. He has brown eyes and short, light-brown hair.
He was wearing a dark-blue jacket with a hood, tan-coloured cargo shorts and blue flip-flops when last seen.
Peloso married former deputy premier George Smitherman six years ago. They later adopted children together.
"I regret to confirm that Christopher Peloso has been missing from our home for almost 24 hours," said Smitherman in a statement, adding he hopes his husband and father of his children "will be home safely soon."
Smitherman served an MPP at the Ontario legislature for more than a decade. Under former premier Dalton McGuinty, Smitherman held several senior cabinet roles including deputy premier, health minister and energy minister.
Smitherman later exited provincial politics and made a run for mayor of Toronto.
Anyone with information about Peloso is asked to contact police at 416-808-1300, or to call Crime Stoppers at 416-222-8477.