Pasadena Police Lt. John Luna said the robbery happened at about 6:22 p.m., when the man, in his 30s, entered the bank and handed a teller a note demanding money.
The suspect was about 5 feet 9 inches tall and was wearing a black hoodie and beanie. Witnesses said he had a short beard.
Luna said the man escaped and ran through the parking lot toward Washington Blvd.
Officers are continuing to investigate. Luna said no weapon was used in the robbery.