Background <p>Proximal humeral fractures are common injuries in the elderly population, with their incidence expected to rise due to increased life expectancy. A small subset of these fractures may be associated with dislocating forces that can result in shoulder dislocation concurrent with the fracture. For the elderly patients, proximal humeral fracture dislocation can be treated by open reduction and internal locking plate (LP) fixation or reverse shoulder arthroplasty (RSA). By now, no high-quality trials have compared the two.</p> Methods <p>This study is a prospective, single-center, superiority randomized controlled trial (RCT) comparing RSA and LP fixation in elderly patients (aged 65 to 85 years) with a proximal humeral fracture dislocation. Eligible participants will be randomly assigned to either the RSA or LP group (1:1 ratio). Postoperative follow-up will be conducted at 1&#xa0;day (in the ward), 1 month, 3 months, 6 months, 12 months, and 24 months after surgery. Primary outcome is the Constant-Murley Score at 1-year postoperatively. Secondary outcomes include short version of Disabilities of the Arm Shoulder and Hand questionnaire score, American Shoulder and Elbow Surgeons score, Visual Analog Scale score, EuroQol-5 Dimension score, range of motion, strength and postoperative complications.</p> Discussion <p>This trial is the first RCT comparing RSA with LP fixation for proximal humeral fracture dislocations in elderly patients. The results of this study will provide high-quality evidence to guide clinical practice.</p> Trial registration <p>China Clinical Trials Registry No. ChiCTR2400088249.</p>