Although lipomas are the most common mesenchymal tumors, the intramuscular type is rare. We report the case of a patient with rotator cuff arthropathy with a lipoma in the teres minor. Wide surgical excision and total shoulder arthroplasty with reverse prosthesis was performed and 18 months of follow up showed excellent results with any recurrence. The teres minor is extremely important for the proper function of a reverse prosthesis, and lipoma growth in the muscular belly can compromise the functionality of the prosthesis. To the best of our knowledge, this is the first case report of a rotator cuff arthropathy with a lipoma in the teres minor.