Background Proximal humerus fractures (PHFs) are relatively common, although optimal rehabilitation is unknown. This review aims to characterize the published rehabilitation regimens utilized for PHFs. Methods A systematic review was performed per PRISMA guidelines, utilizing PubMed/MEDLINE, Embase, and Cochrane. All studies reporting PHF rehabilitation protocols after nonoperative management, open reduction internal fixation with a plate, or intramedullary nailing were included. Results Forty articles comprising 3507 patients (66% female, weighted mean age 63.5 years) were included. Substantial variability was present regardless of management. Rehabilitation modalities reported were: sling use in 34 cohorts, most commonly for three weeks; pendulum exercises in 21 cohorts, most commonly starting at post-intervention day 1; post-intervention passive range of motion (ROM) for 30 cohorts, most commonly starting at two days; active-ROM in eight cohorts, most commonly starting at three weeks; active-assisted ROM for 21 cohorts, most commonly starting at three weeks; unlimited ROM for 20 cohorts, most commonly at 4 or 6 weeks; non-weight-bearing for six cohorts, most commonly for six weeks; strengthening for 16 cohorts, most commonly at six weeks; removal of all restrictions for nine cohorts, most commonly starting at six weeks. Conclusions Published rehabilitation protocols for PHFs vary considerably regardless of management. Future studies comparing methods of management need to consider the influence of postoperative rehabilitation protocol heterogeneity when aggregating data from multiple sites. Level of Evidence IV