The robbery happened at around 6.40pm on Friday at the William Hill shop on Maryhill Road.
The suspect threatened staff with what appeared to be a firearm and demanded money.
Police said no firearm was discharged and no one was injured, however the two staff members - a 20-year-old woman and a 21-year-old man - were "badly shaken".
The man is described as white, 5ft 11in and of slim build. He was wearing a black hooded top with a white zip, black jogging trousers and white trainers. He had a black scarf wrapped around his face and was carrying a drawstring bag.
Detective Constable David Somerville, of the Greater Glasgow Division's robbery unit, said: "Maryhill Road is a particularly busy area and I am sure that there are motorists or pedestrians that may have seen this man acting suspiciously near the bookmakers."