The collision happened around 6:30 p.m. in the 12300 block of Long Beach Boulevard.
The deputy's cruiser at the scene had visible damage to its windshield.
The pedestrian was brought to a local hospital to be treated for injuries.
The northbound lanes of Long Beach Boulevard were closed in the area during the investigation.
The sheriff's department said the cruiser had its lights and siren going as it was responding to a call at the time of the collision.
The deputy was also transported to the hospital.
The circumstances of the collision were under investigation.