A vehicular lane change system includes a forward-viewing camera that has a field of view through the vehicle windshield that encompasses a road being traveled along by the vehicle. Responsive at least in part to processing of image data captured by the camera, a control determines the lane traveled by the vehicle. The control is operable to detect a lane change maneuver of the vehicle to a lane immediately adjacent to the lane traveled by the vehicle. Detection of the lane change maneuver is based at least in part on vehicle steering data and/or image processing of captured image data. Responsive to the control detecting the lane change maneuver of the vehicle when the driver of the vehicle has neglected to turn on an appropriate turn signal indicator of the vehicle, the control automatically turns on the turn signal indicator at the appropriate side of the vehicle.