Masked men broke into an office at the Warner Village Cinema on Saturday night.
They threatened staff with what appeared to be a gun and used a cosh-type weapon.
The raiders escaped with a large amount of cash but were captured on CCTV inside the building.
The robbery happened at the Corner House complex at 2330 BST on Saturday, when the area would have been filled with people.
Two men managed to gain entry to a private area in the cinema where they attacked the manager with a cosh, and threatened him with what is thought to be a gun.
The man was taken to the Cash Office where he and two other colleagues were made to lie on the floor and their hands and ankles tied up.
None of the members of staff were badly hurt, although two suffered bruising.
Balaclava hood
One of the attackers, who wore a balaclava, also had tape around his ankles, wrists, mouth and eyes, so no bare skin was visible.
Police say many people would have been around the Corner House complex at the time of the armed robbery, and are urging witnesses to come forward.>