Objective To evaluate the cl inical and radiological outcomes of minimally invasive plate osteosynthesis (MIPO) with locking compression plate (LCP) in the treatment of proximal humeral shaft fracture. Methods From July 2004 to April 2008, 26 patients with displaced fractures of the proximal humeral shaft were recruited, including 8 males and 18 females. Age of patients averaged 66 years old (range, 34-82 years old). According to AO classification, there were 4 cases of type A1, 2 cases of type A2, 8 cases of type B1, 4 cases of type B2, 2 cases of type B3, 4 cases of type C1 and 2 cases of type C2. The time from injury to surgery averaged 2 days (range, 1-5 days). There were 8 osteoporotic fractures. Results All surgical wound healed primarily, and there was no wound infection. Three patients had postoperative radial nerve neurapraxia, which recovered at 4, 6, 8 months respectively. All patients were followed up for 6-24 months with an average of 14.1 months. Radiological examination revealed bony union within 6 months in 25 cases. There was 1 delayed union which remained asymptomatic and eventually healed at 8 months with acceptable Constant-Murley score. There were 3 cases of shoulder impingement syndrome diagnosed at 3 months post-operatively. After implant removal, they all achieved an acceptable Constant-Murley score. According to Constant-Murley scoring system, there were 11 excellent, 10 good and 5 acceptable results. The excellent or good rate was 80.8%. Conclusion MIPO technique using LCP is an effective method to treat proximal humeral shaft fractures, which facil itates functional recovery of the shoulder joint. During the surgery, it is important to achieve a good fracture reduction and to avoid compl ications.