Our objective was to evaluate the locking plate osteosynthesis (OS) results in treating three- and four-part humeral fractures in patients older than 65 years. Twenty-eight patients who underwent plate osteosynthesis for proximal humerus fracture between 2017 and 2021 and had at least one year of follow-up were included in the study. The Constant-Murley shoulder score (0-55 points: poor, 56-70 points: moderate, 71-85 points: good, 86-100 points: very good), shoulder motion in all directions, pain, and performing daily activities of daily living at postoperative follow-up of the shoulder range of motion was also assessed. The mean age of our patients was 75.14 (66-94). The mean follow-up time was 58.8 (18-73) months. One of our patients developed avascular necrosis in the humeral head, and two of our patients underwent partial shoulder arthroplasty when union could not be achieved. Graphic follow-up revealed that the plate caused subacromial compression in 5 patients, that the locking screw loosened in 3 patients, that 1 (3.22%) screw in the humeral head migrated into the joint in 3 patients in the postoperative period, and that the humeral head fused in varus position in 6 patients. In 3 of our patients, the screws that had migrated into the joint were removed. Hemiarthroplasty was performed in one patient with avascular necrosis and two patients with nonunion. The mean Constant-Murley shoulder score was calculated to be 49.74 (23-98). It was considered excellent in 2 (6.45%) patients, good in 2 patients, moderate in 6 patients, and poor in 18 (67.74%) patients. Infections, vascular and nerve damage did not occur in our patients. Considering osteoporosis in three-part and four-part fractures of the proximal humerus of Neer, the results of plate osteosynthesis treatment are not successful in patients with advanced age, additional morbidity and high surgical risk.