He has struck three times since late October, one each in Auburndale, Sunnyside and Astoria.
According to police, he hasn't used a weapon. He gives tellers a note demanding cash, and in two cases he got away with some.
He has stolen at least $3,000.
Police have released surveillance photos of the suspect, who is described as a white male wearing a white hat, gray sweatshirt and carrying a black backpack.
No one was injured in any of the robberies.