Four cases of tardy ulnar nerve palsy associated with a cubitus varus deformity of the elbow secondary to a supracondylar fracture of the humerus are presented. All patients had surgical management of their ulnar nerve palsy. In two patients, the ulnar nerve was entrapped by scar tissue at the abnormal position and the nerve developed a sharp V-shaped kink when the elbow was flexed. In one patient, the ulnar nerve displaced anteriorly with elbow flexion and spontaneously reduced into the ulnar nerve groove with elbow extension. In one patient, the ulnar nerve remained in the ulnar nerve groove; however, it was entrapped by fibrous bands arising from the flexor carpi ulnaris. It is speculated that malunion resulting in cubitus varus deformity will alter the anatomy at the elbow and that this can have a direct effect on the position and instability of the ulnar nerve. Incongruity of the elbow joint due to cubitus varus deformity also may cause osteoarthritis changes. As a result, ulnar neuropathy may develop from irritation to the ulnar nerve from the posttraumatic osteoarthritic changes at the elbow joint.