Longstanding humeral shaft nonunion is uncommon because humeral shaft fractures often respond well to conservative and surgical treatments. However, when it occurs, the treatment of longstanding humeral shaft nonunion is challenging. This study is a retrospective analysis of the clinical and radiographic findings in a consecutive series of patients with longstanding humeral shaft nonunions who underwent locking compression plate (LCP) fixation and autogenous iliac crest bone grafting.Six patients were surgically treated at Xi'an Hong Hui Hospital for longstanding humeral shaft nonunions between February 2011 and June 2015. Four patients were of synovial pseudarthrosis, 1 was atrophic, and 1 was hypertrophic. Follow-up was for at least 12 months after intervention. Standardized treatment included a thorough debridement, LCP and screw fixation, and autogenous iliac crest bone grafting. In 3 patients, a single plate was applied, and in the other 3 patients, double plates were used. The main outcome measurements were shoulder and elbow function (Constant and Murley scale, and Mayo elbow performance index [MEPI]) and the visual analog scale (VAS) for pain. In addition, all complications were documented.Our series included 6 male patients with an average age of 56.3 years and an average nonunion duration of 19.5 years. All patients had previously undergone at least 1 operation. At a mean of 26 months follow-up, all fractures had achieved solid union and none of the implants had evidence of loosening or breakage. Postoperative alignment was within 10° of anatomic in 4 patients, 1 patient had 23° of valgus angulation, and 1 patient had a posterior angulation of 12°. Mean humeral shortening was 2.8 cm. The mean Constant and Murley joint function score was 88.3 points, the mean MEPI was 96.7 points, and the mean VAS was 0.7. All patients reported significant improvement in shoulder and elbow function, and each patient was able to resume work and was satisfied with the treatment.Plate fixation combined with autogenous iliac crest bone grafting is an excellent option for the treatment of longstanding humeral shaft nonunion.