All of the alleged assaults took place on a TTC bus, dating back to this summer with the latest occurring on Thursday.
The route was from North Etobicoke to Kipling Station during the morning rush hour. Police say the female victims were aged 18 to 25.
Sean Stewart, the suspect, was not known to the women.
Police have laid four charges of Sexual Assault. The suspect appeared in court Friday morning.
Police believe there may be more victims.
Anyone with information is asked to contact police at 416-808-7474, Crime Stoppers anonymously at 416-222-TIPS (8477), online at 222tips.com.