The first robbery was reported at about 2:50 p.m. Friday on North Main Street near Parkside Drive, police said.
The victim reported walking down the street when a suspect approached him, brandished a handgun, and demanded his property. The suspect then fled in a vehicle driven by a second suspect.
The suspect was described as a black male in his teens or early 20s who is about 5 feet 9 inches tall and 160 pounds with a thin build. He was last seen wearing a black hooded sweatshirt, dark blue baggy jeans, and had short hair and a moustache.
The suspect vehicle was described as a newer-model dark gray or blue Toyota sedan, possibly a Camry, with orange paper "Berkeley" dealer license plates, according to police.
About 40 minutes later, at 3:30 p.m., another robbery was reported on South California Boulevard near Bonanza Street, police said.
The victim reported a similar series of events in which a suspect approached, brandished a handgun, and demanded his property before fleeing in a vehicle.
The suspect and vehicle descriptions were similar to the ones given in the first robbery, according to police.
No one was injured in either robbery.
Anyone with information about the cases is encouraged to call Walnut Creek police at (925) 943-5844.