CCTV images show Michael Slaven, from Dumbarton, was last seen at St Enoch subway station at around 2am on Friday.
The 23-year-old electricia had been out with friends but left the Sugar Cube nightclub in Queen Street alone.
He did not return to the home he shares with his mum Elaine, 53, and siblings.
Police Scotland officers are scouring CCTV footage and carrying out "extensive enquiries" into the disappearance, which is said to be highly unusual.
His dad John Slaven, 52, said: "This is not like Michael. He hasn't used his bank card or phone since he went missing. He calls his mum to let her know where he is all the time.
"He seemed to be acting a bit odd on the CCTV pictures so if anyone knows where he is we would ask that they get in touch."
Michael was last seen wearing a white T-shirt with a printed photo, and light green jeans.
Anyone with information is asked to contact Dumbarton Police Office on 101."