The robbery was reported at about 8:25 p.m. at the restaurant in the 2400 block of N. Main Street, according to police.
The three suspects entered the store and a suspect armed with a gun stayed in the dining area while the other two suspects went behind the counter and opened the cash registers with a code, police said.
The suspects took cash from the registers and put them in bags before leaving the area headed northbound on N. Main Street in a dark brown or black four-door Mazda, according to police.
No injuries were reported from the incident.
Police are describing two of the suspects as men who are between 6 feet and 6 feet 2 inches tall who had thin builds and wore black hooded sweatshirts and black pants. One of those two men also wore a mask similar to the one used in the movie "Scream."
The third suspect, who carried the small handgun, is described as a man who is about 5 feet 6 inches tall with dark skin and was wearing a black sweatshirt and black bandanna, according to police.
Anyone with information about the robbery is encouraged to call the Walnut Creek Police Department at (925) 943-5844.