In this randomized controlled trial, 34 patients with Neer 4-part proximal humerus fractures (aged 50-75) were randomly assigned to receive either plate osteosynthesis with a vascularized pectoralis major graft (Group A, n=17) or tricortical iliac grafting (Group B, n=17). The primary outcome was reduction loss, and secondary outcomes included humeral parameters (humeral neck shaft angle, humeral head height, avascular necrosis) and functional assessments (Constant Score and American Shoulder and Elbow Surgeons score). Group A showed significantly less reduction loss (17.6% vs. 58.8%, P=0.013). There was a lower rate of humeral head avascular necrosis in Group A (5.8% vs. 29.4%, P=0.071) than in Group B, which trended towards statistical significance. Constant scores were not statistically significant between groups. American Shoulder and Elbow Surgeons scores were statistically higher in Group A at 3, 6 and 24 months post-procedure. Thus, the technique with the pectoralis major graft demonstrated favorable clinical and radiological results without additional donor site morbidity, suggesting its potential advantages in treating Neer 4-part proximal humerus fractures.