Periprosthetic fractures of the humerus complicate 2-4% of total shoulder arthroplasties. Intraoperative fractures are more common than those that occur after surgery and are usually the result of faulty surgical technique. Patients with osteoporosis are at increased risk for periprosthetic fracture of the humerus, and these injuries are most common in patients with rheumatoid arthritis. Common mechanisms of intraoperative fracture include excessive external rotation forces because of poor operative exposure, improper starting hole location, and too forceful impaction. Intraoperative fractures should be stabilized with cerclage wires, and long-stem implants should be used if the fracture involves the shaft of the humerus. Postoperative fractures frequently compromise the functional abilities of the patient; operative treatment seems to give the best results. Treatment is based on a classification of the fracture, accounting for the location of the fracture and whether the prosthesis is stable or loose. Postoperative fractures of the distal humerus that are extra-articular may be safely treated nonoperatively.