Background Proximal humeral fracture is the third most common fracture in elderly people after fractures of proximal femur and distal radius. They typically occur after low-energy trauma in women affected by osteoporosis, bilateral involvement is rare and usually with a simple pattern of fracture. Bilateral four-part proximal humerus fractures are even less frequent, with only a few reports published previously, with all of them caused by a seizure or electrocution in patients < 65 years old. Case presentation We present a 77-year-old right-handed female that sustained a bilateral simultaneous four-part humeral fracture secondary to accidental slip-and-fall occurred at home. Patient was treated with simultaneous bilateral Reverse Shoulder Arthroplasty (RSA) in our structure. Functional assessment was undertaken at 6- and 12-months follow-up (FU) after surgery, using the Constant-Murley score (CMS) and the Disabilities of the Arm, Shoulder and Hand (DASH) score. Outcome The simultaneous RSA procedure was well tolerated by the patient. Post-operative course was optimal with relatively low blood loss, rapid functional recovery, and fast pain relief. The CMS and DASH score were reasonably good at 6-months FU (right-left: 39–57 and 50.8–30.5, respectively) and they further improved at 1-year FU (right-left: 66–82 and 35.8–19.2, respectively). X-rays showed good position of the implants with no evidence of scapular notching at 1 year. Patient rated the overall satisfaction as good. Discussion Bilateral four-part proximal humeral fractures are complex injuries difficult to manage. Optimal treatment is controversial, and it can be conservative or surgical, varying from open reduction and internal fixation (ORIF) to arthroplasty. However, this last option is still directed to only one side, preferring ORIF or conservative treatment for the contralateral. In case of comminute and displaced fractures, low bone quality, rotator cuff deficiencies and eccentric osteoarthritis, RSA is to prefer as a surgical option. For these reason, in selected cases of bilateral four parts proximal humerus fracture, especially when occurs in elderly patients, the simultaneous RSA implantation can represent a valid option to achieve an adequate functional result and a fast recovery. This is the first description, to our knowledge, in English literature of a simultaneous bilateral RSA.