Bennett's fractures are the most common fractures around the trapeziometacarpal joint but require specialized radiographs to be correctly diagnosed. If a fracture is missed at initial presentation, it may heal with an intra-articular gap, leading to joint incongruency and a painful trapeziometacarpal joint. We present a new technique to correct the intra-articular gap and restore joint congruency in the event of a symptomatic Bennett malunion with a gap of at least 2 mm. The joint is exposed through an anterolateral approach, and the malunion is marked with K-wires under fluoroscopic control. A closing wedge osteotomy with excision of the malunion site is then performed to restore joint congruency. The osteotomy is fixed with 3 interfragmentary screws, and the joint is immobilized for 2 weeks before passive mobilization is initiated. Hardware can be removed between 3 and 6 months postoperatively after consolidation of the osteotomy. We recommend this technique in active patients without trapeziometacarpal osteoarthritis who present with a painful Bennett malunion. Restoration of the joint congruency reduces pain and may prevent the development of posttraumatic osteoarthritis.