Background: There are several techniques for treatment of humeral shaft fractures. The purpose of this study was to evaluate the outcomes of fixation of humeral shaft fracture with minimally invasive plate osteosynthesis.Methods: Ten patients (7 males, 3 females) with traumatic humeral shaft fracture were included in this prospective study. The meas age of patients was 31.7±9.8 (16-51) years. According to OTA classiciation, there were one case of A1, two cases of A2, three cases of A3, three cases of B2, and one case of C2 type. The mean distance measured from the fracture site to elbow joint was 7.7±3.11 (4.5-13) cm. Two patients had radial nerve contusion. All fractures were treated in a minimally invasive way. The function of elbow and shoulder were assessed by MEPS and UCLA scores. The mean time of follow-up was 9 months.Results: The mean maximal final angulation was 7.7±3.2°. The final rotational alignment was within normal limits, with no shortening in all cases. One patient needed second surgery and bone grafting because of delayed :::union:::. The mean UCLA score was 34.2±1.2 and the mean MCPS score was 97±6.3. There was no postoperative radial nerve injury. The 2 cases of radial nerve contusion recovered 4 and 4.5 months postoperatively. Conclusion: MIPO is a safe method in the treatment of humeral shaft fracture with a minimum lesion to soft tissue with a high :::union::: rate. It is suggested that minimally invasive plate osteosynthesis be considered in the treatment of humeral shaft fractures.