A suspect has not yet been apprehended.
The Mission Federal Bank on W. Washington Street was the scene of an armed bank robbery at about 9:30 Thursday morning.
Police say a man of unknown race entered the building with a handgun and demanded cash from the teller.
The teller complied and gave the suspect an undetermined amount of money before he fled.
Police describe the man as wearing a gray "beanie" cap, a gray hoodie, dark sunglasses and a mask.
San Diego Police Robbery Detectives and the FBI are handling the investigation.