Background:Previous observational studies and meta-analyses have recommended augmentation with a fibular allograft (FA) during the treatment of proximal humeral fractures with locking plates (LPs). However, to our knowledge, randomized controlled trials comparing open reduction and internal fixation (ORIF) with and without FA have not been performed to date.Methods:This was a randomized controlled trial in which adults with a medial column comminuted proximal humeral fracture were randomly allocated to undergo ORIF with an LP (the LP group) or with an LP augmented with an FA (the FA group). Patients were followed for 24 months. The primary outcome was the Disabilities of the Arm, Shoulder and Hand (DASH) score at 12 months after the surgical procedure. The secondary outcomes included the DASH score at other time points, shoulder function, pain score, satisfaction, complications, and changes in neck-shaft angle and humeral head height.Results:From October 20, 2016, to December 24, 2019, 80 patients were randomized. There were 52 women (65%), and the mean patient age (and standard deviation) was 65 ± 14 years. Of the 80 patients, 39 were allocated to the FA group and 41 were allocated to the LP group. At the primary time point (12 months), the unadjusted mean between-group difference in DASH score was −1.2 (95% confidence interval [CI], −7.3 to 5.0; p = 0.71) favoring the FA group, and, with adjustment for smoking, alcohol drinking, and diabetes, the between-group difference was −1.4 (95% CI, −7.7 to 5.0; p = 0.67) favoring FA. No significant differences between the 2 groups were found among the secondary outcomes.Conclusions:No additional benefit was found for FA augmentation in treating medial column comminuted proximal humeral fractures.Level of Evidence:Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.