A pivot head wrench includes a handle, a switch, a pusher, a position-retaining device including a resilient member, a pawl, and a driving head. The pivot head wrench is switchable between lock and unlock modes. In the lock mode, the switch is rotated to a first position, and the pusher is abutted against the pawl, and the driving head is adapted to be pivoted at various positions, and the pawl is temporarily disengaged from the driving head when the driving head is pivoted from one position to another and engagement therebetween is resumed by the resilient member thereafter. In the unlock mode, the switch is rotated to a second position, and the switch is abutted against the pawl such that the pawl is restrained from movement and from disengagement from the driving head, and the driving head is restrained and securely held in place at a selected position.