Police were alerted to the robbery, which appeared to involve one person, at the TAB on Hillside Rd about 4.40pm.
Cash was taken from the premises, a police spokeswoman said.
An eyewitness to the police arriving said he had seen a police car pull up and three police enter the building.
At 5pm, an ODT reporter saw police allowing three people, who were presumed to be punters, out of the TAB.
One man, who had been inside during the incident, said he had slept through the entire ordeal, but understood that there had been a robbery.
A worker at a nearby store said he had seen two men, one older and one younger, loitering near the scene prior to the robbery.
Investigations were ongoing, a police spokeswoman said.
A police spokeswoman said despite two offenders entering the St Kilda Tavern and only one entering the TAB, police remained open minded in regards to the two offences being related.
Police ask anyone with more information to call 105 or anonymously via Crimestoppers on 0800 555 111.
