Periosteal sleeve fractures, or avulsions of cartilage and/or periosteum with or without an osseous fragment in skeletally immature individuals, are notoriously easy to miss and a high index of suspicion is necessary for accurate diagnosis and treatment. While periosteal sleeve avulsion fractures are classically reported in the patella, they have also been reported in the shoulder, clavicle, and elsewhere in the knee. However, no published reports exist for a periosteal sleeve avulsion fracture in the hand. This case details the first reported instance of such an injury involving a thumb metacarpal in a 3-year-old boy, treated with open reduction and percutaneous pinning of the thumb metacarpal.