The woman was walking south along Burrard Street at around 7:30 p.m. PT, when she was tackled to the ground and assaulted.
She defended herself, and broke free after biting her attacker, who released his hold and ran away, eastbound on Davie Street towards Granville Street.
"The events that happened that night are extremely serious, this woman is extremely traumatized," said Vancouver Police Sgt. Randy Fincham.
"But she was able to fight back and scream and call for help and fend off this attacker before he managed to progress any further with this attack," he said.
The suspect is an Asian man in his 30s, five feet four inches tall, with a slender build and dark hair. He was wearing a dark shirt, light-coloured jeans and was carrying a bright yellow backpack at the time of the attack.
Anyone with any information about the attack, or who may know the identity of the suspect, is asked to call the Vancouver Police Sex Crimes Unit at (604) 717-0602 or to remain anonymous, contact Crime Stoppers.