Melbourne Sexual Offences and Child Abuse Investigation Team detectives have arrested a man following a sexual assault at Federation Square in May.
The incident happened in toilets near the building off Flinders Street around 2pm on Wednesday, 5 May.
Two 15-year-old girls were in the toilets when they were allegedly sexually assaulted.
Investigators arrested a 21-year-old man at a Croydon address this afternoon.
He is currently assisting police with their enquiries.
Anyone who recognises the man is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au