We present the case of a femoral head malunion with lateral cephalic femoroacetabular impingement managed by arthroscopic osteotomy/takedown, bone grafting, internal fixation, and cephaloplasty. The treatment rationale and surgical technique are presented. A successful outcome at 3 years was obtained with radiographic evidence of union without osteonecrosis. Even beyond acute femoral head osteosynthesis, arthroscopic surgery may enhance the ability to treat femoral head malunions. Moreover, arthroscopic osteosynthesis may address lateral cephalic FAI, a previously unreported condition.