A man walked off with some €1,500 after a hold-up at a lotto office close to the Lidl Supermarket in Sta Venera at around 5.15 p.m.
The police said the man, who was wearing black, was hooded and carried a firearm.
He is understood to have left the scene of the crime on foot.
The lotto booth holder, a 60-year-old man from Hamrun, was under shock but unharmed.