The suspect, who was wearing an old Domino's delivery jacket, robbed the restaurant's till, a delivery driver, and a customer before locking all three in the bathroom.
Police are not disclosing how much money was taken or if the suspect may have been an employee, but say the incident is reflective of the dangers night workers face.
Police are describing the suspect as a white male in his 30s with brown hair and a mustache.
He was last seen fleeing the restaurant on foot.
Anyone with information is asked to call the sheriff's detectives at 839-4777.