The political veteran — who retired from the city's top job last year — was among those who relayed the torch through the area to a rain-soaked celebration at Port Credit Memorial Park.
McCallion arrived by boat on the Credit River shortly after noon, before passing the flame to the next runner.
"I'm soaking wet," she said later to reporters, with a laugh. "But so what? I don't mind getting wet to have the privilege and honour of carrying that torch."
McCallion said the games are an important opportunity for athletes from across the Americas to compete.
"We need the opportunity — for young people to excel," she said.
The torch is nearing the end of its 41-day trek, which has covered some 20,000 kilometres by road and air. It will make its final stop at the opening ceremony of the Pan Am Games in Toronto on July 10.