We experienced two cases of ulnar nerve palsy caused by a ganglion that were managed by excision of the ganglion performed concurrently with subcutaneous anterior transposition of the ulnar nerve. Satisfactory results were obtained. The possibility of ulnar nerve compression by ganglion must be considered in patient who complains rapidly progressing ulnar nerve palsy. For those cases, ultrasonography or magnetic resonance imaging seems to be helpful in obtaining preoperative diagnosis.