It happened in 2500 block of Cheltenham Avenue.
Witnesses say the suspects were wearing hoodies when they walked into the Laundry Depot Center at 4:20 a.m. Friday.
One of them had a gun and knocked the male attendant and a female customer to the floor.
The bandits handcuffed the attendant, then broke into the ATM.
They made off with an undisclosed amount of cash.
There were no reports of injuries.