A valve timing system for an internal combustion engine includes a phase alteration mechanism interposed between a driving rotator and a driven rotator and having a direction turning point at which the phase alteration direction is reversed when a movable portion of the mechanism travels from a beginning to a termination, and an operation control device for displacing the movable portion when undergoing an energization control, the movable portion being displaced toward the beginning when the energization control fails to be carried out. The rotation phase is set at a middle position between a maximum retard position and a maximum advance position when the movable portion is located at the beginning.