According to the Toronto Police Service (TPS), the girl was approached by the suspect on August 29, around 6:30 p.m., at a store near Dixon Road and Islington Avenue.
Police say the man spoke to the girl, grabbed her arm and then sexually assaulted her.
The girl told staff what happened and they then contacted the police.
TPS describes the suspect as a 6′ tall man in his 20s with a thin build and pierced ears.  He was last seen wearing a red hoodie, black baseball cap and black shoes.
Police say the suspect fled in a four-door silver Toyota sedan.
Police are asking anyone with information about the incident to call them at 416-808-7474.  Anonymous tips can also be provided through Crime Stoppers at 416-222-TIPS (8477) or online at www.222tips.com.