The suspect entered the Castle Newsagents in Dumbarton Road at around 8.20am on Wednesday, July 30.
He threatened the male shop worker with a knife before making off with a three figure sum of cash.
Police say the shop worker was uninjured but badly shaken as a result of the robbery.
Police Constable Eilidh Gordon, of the Robbery Unit based at Pollok Police Office, said: "Immediately after the robbery, whilst making off from the scene, the suspect dropped a high viz jacket and black item of clothing.
"The suspect retrieved the high viz jacket but the black piece of clothing was left on the pavement outside Castle Newsagents, Dumbarton Road.
"The suspect was thereafter seen getting into a small black car outside Ladbrokes Shop, Dumbarton Road a short distance from the scene.
"I would ask anyone who saw this man acting suspiciously in the area of Dumbarton Road or has any knowledge of any person retrieving the black item of clothing left on the footpath on Dumbarton Road around the time of the robbery on Wednesday morning to come forward to police."
The suspect is described as white and he 17 to 23 years old.
He is 5' 10" and of slim build. He was wearing a grey tracksuit with the hood up and carrying a black JD coloured carrier bag over his back.
Anyone with information that may assist this investigation should contact Police Scotland on 101. Alternatively Crimestoppers can be contacted on 0800 555 111, where anonymity can be maintained.