Adamantinoma is a rare primary bone tumor occurring in the mandible and the long tubular bones. The diaphysis of the tibia is the most common site of extragnathic presentation. Fibular involvement is rare and usually has coexisting tibial involvement. Adamantinoma arising in the distal fibular metaphysis has not been previously reported. This is a case of a teenage boy presenting with a cystic lesion of the distal fibula, initially diagnosed and treated as a unicameral bone cyst. Aggressive behavior ultimately led to a diagnosis of adamantinoma. He was treated with distal fibulectomy without surgical reconstruction with good functional outcome.