Medial condyle fracture of the humerus is extremely rare in pediatric elbow fractures. We report a rare case of malunion of medial condyle fracture in a 10-year-old boy who had an injury on the right elbow at age 4. He was referred to our clinic because of severe varus deformity (the carrying angle was 191°, unaffected side 172°) with instability. Extra-articular closing wedge osteotomy was performed. Five years after surgery, the carrying angle was 172° and the patient had no pain and no difficulties with activities of daily living.