The victim had been with her child in a red pushchair when she was approached by a man at the ticket machine, who made some abusive remarks.
The man - whom the woman knows - then followed her onto Platform 4 to board the 4.20pm train to Glasgow Queen Street Station.
As the train left the station, the man assaulted the victim before a female passenger intervened. Officers are now appealing for witnesses to the incident, which happened on Monday, April 13.
The man is 27 years old and is described as white, 5ft 8in to 5ft 9in, of slim build, dark brown hair short cropped hair, dark brown full beard, wearing a black leather jacket with fabric sleeves, chunky white or cream jumper and dark jeans.
Anyone with information should call 101.