Aim: Proximal humeral fractures are approximately 5% of all fractures and, % 15-20 is displaced and unstable. By the introduction of locking plates there used to be a substantial rise in the osteosynthesis of the 3 and 4-part proximal humeral fractures. But there is still a lack of consensus for the optimal treatment of these complex fractures. In this retrospective study, we aimed to evaluate the functional outcomes and prognostic factors of 3 and 4-part proximal humerus fractures treated with locking plate osteosynthesis in elderly. Material and Method: 53 patients with displaced 3 and 4-part proximal humeral fractures treated with locking plate osteosynthesis between 2010 and 2015 were included. The fractures were classified according to Neer classification system. Outcomes were assessed by Constant-Murley scoring system (CMS), visual analog pain scale and plain radiographs. In reference to range of motion, forward elevation and abduction of the arm were measured. Results: No statistically significant differences found between the 3-part and 4-part fractures in CMS, forward elevation and, abduction (p>0.05). Pain was significantly higher in 4-part fractures (p=0.035). CMS, forward elevation, and abduction were inversely correlated with age and delay in surgery. There was statistical significance between the patients had complications and those not in terms of CMS, forward elevation and, abduction (p=0.029, p=0.017 and p=0.024). Discussion: Functional outcomes of locking plate fixation of proximal humerus fractures are associated with patient related factors, fracture pattern, surgeon and, the implant. When indications are carefully selected, locking plate osteosynthesis yield good outcomes in surgical treatment of 3 or 4-part proximal humerus fractures.