Objectives: To document union rate, complications and patient-reported outcomes following open reduction and internal fixation (ORIF), with and without bone grafting (BG), for humeral diaphyseal nonunion following failed non-operative management. Design: Retrospective. Setting: University teaching hospital. Patients and intervention: From 2008-2017, 86 consecutive patients (mean age 59 years [range 17-86], 71% [n=61/86] female) underwent nonunion ORIF (plate and screws) at a mean of 7 months post-injury (range 3-21.5). Eleven (13%) underwent supplementary BG.Main outcome measurements: Union rate and complications for 83 patients (97%) at a mean of 10 months (3-61). Patient-reported outcomes (QuickDASH, EQ-5D, EQ-VAS, SF-12, satisfaction) for 53 living, cognitively-intact patients (78%) at a mean of 4.9 years (0.3-9.2).Results: Ninety-three percent (n=77/83) achieved union following nonunion ORIF.Complications included recalcitrant nonunion (7%, n=6/83), iatrogenic radial nerve palsy (6%, n=5/83), infection (superficial 7%, n=6/83; deep 2%, n=2/83) and iliac crest donor site morbidity (38%, n=3/8). The union rate with BG was 78% (n=7/9) and without was 95% (n=70/74; p=0.125), and was not associated with nonunion type (atrophic 91%, n=53/58; 4 hypertrophic 96%, n=24/25; p=0.663). Median QuickDASH was 22.7 (0-95), EQ-5D 0.710 (-