The officer was pursuing a suspected drunken driver east on Sonoma Highway near Boas Drive at about 10 p.m. when the bicyclist turned left from the bike lane in front of the patrol car, Sgt. David Linscomb said.
The officer swerved left but was unable to avoid striking the bicyclist, 18-year-old Dylan Debiase, in the No. 1 lane, Linscomb said.
Debiase suffered a broken toe on his left foot and abrasions, and was treated at a hospital and released, Lt. Ben Harlin said. The officer was not injured.
Harlin said the patrol car's lights and siren were off at the time of the collision, and the officer stopped at the scene afterward.
Police shut down the eastbound lane of Sonoma Highway into the early morning hours to investigate the accident.
Anyone who saw the collision is asked to call the Santa Rosa Police Department's Traffic Bureau at (707) 543-3600.