It happened at about 8:30 Friday morning at the intersection of Fresno and G Street in downtown Fresno.
The officer was heading to the federal courthouse to help with reports of a man with a gun.
The officer was driving through the intersection with his lights and sirens on when he collided with another car and hit a traffic light.
Two people in the other vehicle were taken to the hospital with moderate injuries.
Officials closed off the roadway at Fresno and G while they investigated the incident.