Abstract: A stabilizer apparatus for fifth wheel trailers uses a pair of assemblies for placement under front corners of the trailer when parked and leveled. The assemblies each include a leveling jack, a diagonal strut-forming leg, and a connecting chain to secure the jack base and foot of the leg together at a desired location. The top end of each leg has a notch to make contact with a pin securely attached to the underside of the trailer near the area where the top of a jack is located. In operation, each leg is located to extend outward from the trailer with its bottom in contact with the ground and its top contacting a pin on the trailer. By lowering the trailer and taking slack out of the connecting chain, the legs are held rigidly in position by the weight of the trailer, and side movement of the trailer is restrained.