Deputies responded at about 10 p.m. Tuesday to an alarm at a Shell station located at 1667 Woodside Road, where two employees said around $1,700 was stolen from the registers by two suspects wearing black hoodies and black masks.
One of the suspects, who was about 6 feet tall with a slender build, was armed with a silver semi-automatic handgun, according to the sheriff's office.
The second suspect was described as being around 5 feet 7 inches tall with a slender build.
A witness who drove into the gas station parking lot after the robbery said he saw the suspects heading south on Sequoia Avenue.
Sheriff's deputies and Redwood City police searched the area but did not find the suspects.
Anyone with information about the robbery is urged to contact San Mateo County sheriff's Detective Frank Taylor at (650) 363-4363.