The first one happened Tuesday afternoon when an employee from the Great Wall Chinese restaurant was making a delivery to the Brookside Apartments on Willowdale Drive.
Police say a black man showed a gun and took off with the man's cash and cellphone.
The other robbery happened around 10 p.m. on Tuesday night at the Old Town Diner on Route 40.
Police say an employee stepped out of the restaurant to talk with the suspect who then showed a knife, assaulted the individual and got away with an undisclosed amount of cash.
The employee suffered minor injuries.
Anyone with information on the crimes is asked to call Frederick City Police at 301-600-2102.