An unusual case is presented of bilateral, complete digital duplication on the hand of a 9-month-old boy. Radiographic evaluation showed duplication of intact phalanges and metacarpals. Although ulnar polydactyly has been described as one of the most common congenital anomalies of the extremities, it usually manifests itself as a rudimentary skin tag. Ulnar polydactyly can be classified on the basis of genetic, morphologic, and clinical implications. Although polydactyly is reported to occur among approximately 1 in 1000 live births, most of these malformations are rudimentary skin tags. Complete ulnar polydactyly is uncommon; it occurs among approximately 0.014% of all live births. The main goal of surgical treatment of patients with complete-duplication ulnar polydactyly is to establish adequate function. This case report describes the preoperative evaluation and management of complete bilateral duplication of the ulnar digits of the hand.