Transit Crime Investigation Unit detectives are appealing for public assistance after an elderly woman was sexually assaulted at Aspendale Railway Station on 22 September, Victoria Police say.
Investigators have been told an 87-year-old woman holding a walker was waiting for a train on the platform at the station on Nepean Highway about 11.25am.
It is believed an unknown man called out to her and asked if she wanted money and she declined.
He then approached the victim and kissed her on the check before sexually assaulting her.
The woman broke free and boarded the train.
It is believed the offender boarded a Frankston bound train and got off at Carrum Railway Station just before midday.
The offender is described as Caucasian in appearance, facial hair, brown hair and a medium build.
He was wearing a black jacket and blue jeans at the time of the incident.
Detectives have released images of a man that may be able to assist with their enquiries.
Anyone with information is urged to contact Crime Stoppers.