The incident occurred on Sunday at 3 p.m. at the Scott Library on the university's main campus, police said.
The 19-year-old woman was in the library when the man allegedly sexually assaulted her and committed an indecent act, police said.
The woman alerted the university's campus security who located and held him until police arrived.
Henry Kang, 35, of Toronto is facing charges of sexual assault and indecent acts.
He was scheduled to appear in a Toronto court on Monday morning.