The winning film, directed by Britain's Danny Boyle, opens in U.S. theaters on Nov. 28. It tells of a teenager from the Indian slums who wins a chance of becoming a millionaire in a television game show.
The film received an enthusiastic reception from the Toronto audience, and actress Freida Pinto accepted the Cadillac People's Choice Award on Boyle's behalf.
"There are a lot of firsts for me in this," she said. "It's my first premiere, my first time dealing with the press, and now it's my first award.
"Slumdog Millionaire is a film about an underdog who believes in something."
The Toronto festival, where the top award is chosen by the public rather than by industry experts or other insiders, opened on Sept. 4 with Passchendaele, a romance set partly in the mud-filled trenches of World War I.
It closed on Saturday with a gala performance of Stone of Destiny, the story of Scottish nationalists who seek to reclaim the Stone of Scone from London's Westminster Abbey.
Other winners at the end of the festival included Hunger, about IRA hunger striker Bobby Sands, and Disgrace, a father-daughter story based on the bleak Booker prize-winning novel from South African writer J.M. Coetzee.
The top prize at last year's festival was won by Russian mob movie Eastern Promises, which went on to win a best actor Oscar nomination for Viggo Mortensen.
