The robbery was reported at about 7:15 p.m. at the restaurant in the 500 block of Contra Costa Boulevard, according to police.
The suspects allegedly entered the restaurant and immediately began to remove money from the registers, police said.
When they were confronted by an employee, the suspects pointed firearms at her and moved her to the kitchen area of the restaurant, according to police, who say employees in the kitchen were ordered to face away from the suspects and were held at gunpoint.
The suspects ordered the manager to open the restaurant's safe, and fled after taking all the money from the safe and registers, police said.
No one was injured in the incident, police said.
The suspects are all described by police as men who were wearing dark clothing and blue bandanas covering their faces.
Two of the suspects are between 5 feet 7 and 5 feet 10 inches tall and weigh about 150 pounds, while the third suspect is between 5 feet and 5 feet 5 inches tall with a slender build, police said.
An extensive search of the area by Pleasant Hill police, including a K9 unit, and the Contra Costa County Sheriff's Office was unsuccessful.
Anyone with information is urged to contact the Pleasant Hill Police Investigation Division at (925) 288-4600.