This prospective study evaluates the results of a procedure for massive rotator cuff tears that we term reversed arthroscopic subacromial decompression (ASD). The procedure includes an arthroscopic debridement of the subacromial space and glenohumeral joint, an arthroscopic tuberoplasty, and depending on the pathologic condition of the long head of the biceps, a biceps tendon tenotomy. Reversed ASD avoids a classic acromioplasty in order to preserve the integrity of the coracoacromial arch. Twenty-three patients with a mean age of 69 years underwent this procedure. After a mean follow-up of 40 months, the age-adjusted Constant score increased significantly, from 65.9% to 90.6% (P <.001), with 14 excellent, 5 good, 2 satisfactory, and 1 poor result. Preexisting osteoarthritic changes increased significantly but had no impact on the final clinical results. The acromiohumeral distance decreased from 5.1 to 4.5 mm (P =.004). There were no complications directly related to the surgical procedure. When compared with classic ASD studies for massive rotator cuff tears, we obtained similar midterm results with regard to pain relief, functional recovery, and patient satisfaction. We, therefore, conclude that reversed ASD with tenotomy of the long head of the biceps tendon offers a less invasive treatment strategy for massive rotator cuff tears while preserving the integrity of the coracoacromial arch.