Objective To assess the effectiveness of locking compress plate and extra cortical bone bridge fixation for treating atrophic humeral nonunion. Methods Seventeen patients with atrophic humeral nonuninon were treated with locking compress plate and extra cortical bone bridge fixation between November 2006 and June 2015. Of 17 cases, 11 were male, 6 were female, aged 24-63 years (mean, 38.2 years). Fracture located at the left side in 9 cases and at the right side in 8 cases. The mechanism of injury was traffic accident in 13 cases, falling from height in 3 cases, and heavy pound injury in 1 case. The patients underwent surgery for 1 time in 7 cases, for 2 times in 5 cases, for 3 times in 4 cases, and for 4 times in 1 case. The time from fracture to hospitalization was 10-76 months (mean, 22.6 months). The shoulder function was evaluated by Neer score, and elbow function by Mayo score. Results All incisions healed by first intention. Two cases had transient radial nerve symptoms of numbness. All patients were followed up 27.3 months on average (range, 15-60 months). Radiographic examination showed signs of bone remodeling at 6-8 weeks after operation, and formation of extra cortical bone bridge. All of them achieved bone union within 10 to 41 weeks (mean, 17.6 weeks). At last follow-up, the average Neer score was 83.36 (range, 72-96); and the shoulder function was excellent in 10 cases, good in 5, and fair in 2 with an excellent and good rate of 88.24%. And the average Mayo score was 86.52 (range, 68-100); and the elbow function was excellent in 11 cases, good in 3, and fair in 3 with an excellent and good rate of 82.35%. Conclusion The bone bridging could effectively form by extra cortical grafting technique. Atrophic humeral nonunions can be successfully treated with locking compress plate and extra cortical bone bridge fixation.