A control system for an intermediate differential in a four-wheel drive vehicle, the intermediate differential being provided with a lock mechanism which is operated under control of an actuator to selectively maintain the intermediate differential in a locked condition or an unlocked condition. The control system includes a first sensor arranged to detect a steering angle of a dirigible road wheel for producing a first detection signal therefrom when the steering angle exceeds a predetermined value, a second sensor arranged to detect disconnection of the drive power transmitted to the intermediate differential from a prime mover of the vehicle for producing a second detection signal therefrom when transmission of the drive power is disconnected, and a control device responsive to the first and second detection signals from the sensors for controlling the actuator in such a manner that the lock mechanism is operated to release the locked condition of the intermediate differential when the steering angle exceeds the predetermined value in a condition where the transmission of the drive power is disconnected.