The incident was said to have taken place on a No.3 bus from Kingsland Road, Cardonald, to Govan Bus Station on Wednesday, May 14.
No further details were given about the incident.The man is described as white, in his early 30s and of stocky build with a shaved head.
He was wearing a green hooded top, dark tracksuit trousers and red trainers.
A Police Scotland spokeswoman said: "Officers from Govan CID are appealing for anyone who recognises the man in the released CCTV images to contact them."
Information can be given to Govan police office via the non- emergency number 101 or anonymously to the crime-fighting chartiy Crimestoppers on 0800 555 111.