Purpose The aim of this study was to identify specific complications of locking plate fixation of proximal humerus fractures. Patients and Methods Seventy-threee adult patients with a displaced 3- (24%) or 4-part (76%) fracture of the proximal humerus were treated over a period of 2 years under the supervision of a trauma surgeon. Fourty-four patients came back for a clinical and radiographic examinations at least 18 months after the trauma; the others were evaluated at 6 weeks and 3 and 6 months. Results Out of the 73 patients (64.4% females, mean age of 65), 11 patients needed a second surgery and 18 were lost for follow-up after 6 months. Mean final constant score was 62.3 points. The incidence of secondary displacement was 8.2%. Nonunion rate was 5.5%, affecting the constant score ( P = .018). 16.4% of the patients developed a partial necrosis of the humeral head at the latest follow-up, which influenced on the constant score ( P = .029). Quality of the reduction of the greater tuberosity influenced final results ( P = .037). Screw cutout rate was 13.7%, with an influence to the constant score ( P = .001). A too high plate positioning influenced the constant score ( P = .002). Conclusion Locked screw-plates provide more secure fixation of fractures, especially in weak bone. Complications rate remains high. Two complications are to be distinguished: 1) technical complications in plate positioning, length of the screws or secondary screw cutout strongly influence the final clinical result; and 2) specific complications related to this technology such as pseudarthrosis or plate fracture.