Marco Lagrotta, 17, was last seen on Monday at 7:30 a.m. in the city's northwest end, near Church Street and Weston Road.
He is described as white, 5'10", 140 lbs., with brown, curly hair and brown eyes. He was last seen wearing a grey-and-black striped touque, a black bomber-style jacket with white fur-trimmed hood, light-coloured pants, black-and-brown boots and dark glasses.
He was also carrying a black knapsack.
Police are concerned for his safety.
Anyone with information is asked to contact police at (416) 808-1200, Crime Stoppers anonymously at (416) 222-TIPS (8477) or online at www.222tips.com.