Police said the alleged incident happened on the morning of October 22.
A woman was riding a Metro Line 2 train traveling between Jane Station and Woodbine Station when a man sat next to her and allegedly sexually assaulted her.
On Wednesday, police released images of the suspect captured by the train’s surveillance cameras.
He is described as between 18 and 20 years old, five-foot-seven to five-foot-eight and weighs 145 pounds to 160 pounds.
Police said he was last seen wearing a black baseball cap with the Blue Jays logo, a black jacket, a black sweater, black pants, gray and white shoes and a brown camouflage Reebok backpack.
Police are urging anyone who can identify the suspect to contact investigators at 416-808-5300 or Crime Stoppers anonymously at 416-222-TIPS (8477).