A retainer puller including a head with two clamp halves commonly having an opening at their front ends and a handle at their rear ends, and a bolt. The clamp halves are each provided with a hole. The bolt includes a polygonal head and a rod provided with an axial slot of a determined depth across the free end thereof. The rod of the bolt is rotatably secured through the respective holes of the clamp halves. In use, the free end of a retainer is inserted into the opening of the clamp halves and then into the slot of the bolt. By turning the bolt with a wrench, the free end of the retainer may be wound on the rod to reduce the internal diameter of the retainer and thus tighten the retainer on the objects onto which it is fastened.