Aneurysmal bone cysts are non-neoplastic, expansile, osteolytic tumor-like conditions. All bones may be involved, but the most commonly affected is the metaphysis of the long bones, especially the tibia, humerus and femur. We present a 13-year-old female patient with a cystic lesion with cortical continuity and a large bone cyst in the coronoid process of the ulna. The bone cyst was treated with curettage, phenol application and cement implantation following cyst debulking. Aneurysmal bone tumors are rare tumor-like conditions and localization at the coronoid process of the ulna with mechanical block of the elbow motion has yet to be reported. Debulldng and curettage of the lesion and bone cement implantation are useful methods for local control of aneurysmal bone cysts.