An armed man entered the bank at 3005 Alamo Drive around 3:45 p.m., brandished a handgun and demanded money from tellers, Sgt. Todd Dye said.
The suspect is described as a black man, 30 to 40 years old, 5 feet 7 inches to 5 feet 10 inches tall with a slim build, Dye said. He was wearing a white shirt and jeans.
Witnesses in the neighborhood reported seeing a man matching that description, but police didn't find him, Dye said.
Anyone with information about the crime is asked to call Vacaville police at (707) 449-5200 or 449-5214.