The shooting happened about 6:35 p.m. on northbound I-880 south of 98th Avenue, when a man driving a dark-colored sedan fired at the front passenger door of a green Toyota RAV4, striking one of two men inside, according to the California Highway Patrol.
Investigators closed the northbound lanes of the freeway until almost 9 p.m., diverting heavy evening commute traffic onto 98th Avenue.
The driver and passenger were taken to a hospital and the driver is being treated for injuries that the CHP said do not appear to be life threatening.
The shooter is described as a black male in his 30s or 40s, the CHP said.
The CHP is asking anyone who might have information about the shooting to call its investigation tip line at (707) 917-4491.