Malunion of a proximal humerus fracture is difficult to manage once bone union has been achieved in a wrong position. Malunion may be encountered after conservative treatment or internal fixation of fractures, and also around a joint prosthesis. The malunion can involve the greater and lesser tuberosities, humeral head, bicipital groove, or the entire epiphysis. The nature of the malunion must be precisely characterized. Malunion can affect bone structures and the articular surface; any resulting displacements must be carefully measured. Clinical assessments will help to evaluate the functional repercussions and determine the need for correction. Radiographic imaging and CT scan guide the treatment plan. Arthroscopic surgery (acromioplasty or tuberoplasty) can be used to treat biceps tenosynovitis or impingement syndrome in cases where full correction of the malunion is not required. Corrective surgery of a metaphyseal malunion is used to realign the proximal humeral into the proper position. Tuberosity osteotomy is the main predictor for a poor outcome following secondary arthroplasty.