The 26-year-old victim was attacked at the door of the Life O'Reilly pub in Dixon Avenue, Govanhill, at around 11.45pm on Sunday.
The woman's friends had walked into the pub when a man came up behind her and touched her inappropriately.
He fled along Dixon Avenue towards Langside Road after the woman's shouts for help attracted pub revellers.
She did not need hospital treatment but was said to be "very shaken".
The suspect is described as Eastern European, in his mid 20s and about 5ft 7ins.