Non-union of the pediatric lateral humeral condyle following post-traumatic cubitus valgus is a severe complication after inadequate treatment. We report on a then 14-year-old male patient who developed an increasingly defective position in terms of cubitus valgus after conservative treatment of a lateral humeral condyle fracture. After performing screw osteosynthesis and achieving consolidation, a successful supracondylar dome osteotomy was performed which led to relief from pain and free range of motion of the elbow joint.