Bendigo police are investigating a sexual assault which occurred at a Bendigo racecourse last month.

A 58-year-old man was in a bathroom when he was sexually assaulted by an unknown male offender about 4.45pm on 30 March.

The offender fled the scene on foot.

The victim sustained minor injuries.

The offender is perceived to be Caucasian in appearance, aged in his late 30s, medium build with short dark hair.

He was wearing a blue checked shirt with short sleeves.

Police are urging anyone who was in the area at the time or who may have seen the man to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au