Objective To evaluate the effectiveness of locking plates for Neer 3- and 4-part proximal humerus fractures. Methods A retrospective analysis was made on the clinical data of 77 patients with 3- or 4-part proximal humerus fractures, who underwent open reduction and internal fixation of locking plates and were followed up more than 12 months between July 2008 and May 2011. There were 39 males and 38 females with an average age of 54.2 years (range, 18-81 years). Fractures were caused by falling in 47 cases, by traffic accident in 16 cases, by falling from height in 4 cases, by sporting in 5 cases, and by other reasons in 5 cases. The time between injury and operation was 2-16 days (mean, 4.5 days). According to Neer classification, there were 54 cases of 3-part fracture and 23 cases of 4-part fracture. The Constant scores, visual analogue score (VAS), and the complications were evaluated during follow-up. Results After operation, healing of incisions by first intention was obtained in 76 cases and healing by second intention in 1 case. All patients were followed up 12-36 months (mean, 18.5 months). At last follow-up, the Constant score was 71.1 ± 11.9; the results were excellent in 18 cases, good in 24 cases, fair in 25 cases, and poor in 10 cases with an excellent and good rate of 54.5%. The VAS score was 2.8 ± 2.2. Bone nonunion occurred in 2 cases; the other patients had bone union within 2-6 months (mean, 3.2 months). The complications occurred in 25 cases (32.5%). Revision surgery was performed in 15 patients (19.5%). Conclusion The treatment of Neer 3- and 4-part proximal humerus fractures remains challenging. Anatomic reduction, stable fixation, and reduced humeral head blood supply disruption may lead to a satisfactory outcome.