The best surgical treatment for an irreparable rotator cuff tear is controversial. In such cases, partial rotator cuff repair, primarily involving the posterior cuff in most reports, has been shown to be beneficial. The authors retrospectively investigated 41 patients who underwent arthroscopic subscapularis-only repair and greater tuberoplasty between April 2003 and August 2009 for massive 3-tendon cuff tears with irreparable supraspinatus and infraspinatus tendons after 3 months of conservative management was unsuccessful. Twenty-five patients (61%) underwent biceps tenotomy, and the remaining 39% had preexisting biceps tenotomy or rupture. The patients were assessed with American Shoulder and Elbow Surgeons (ASES) and Single Assessment Numeric Evaluation (SANE) scores. Of the 41 patients, 34 (83%) were available for a followup telephone questionnaire after a minimum of 12 months (mean, 35 months; range, 12-84 months). Mean ASES and SANE scores were 76% and 63%, respectively. Mean postoperative passive range of motion was 156° of forward flexion and 39° of external rotation. Of the patients queried, 74% (25 of 34) were able to actively raise their arms above shoulder level. For those with a positive belly-press test result preoperatively, 22 of 27 patients had a negative test result postoperatively. A total of 3 complications (7.3%) occurred. Workers' compensation claim was a strong predictor of lower shoulder scores. Arthroscopic subscapularis-only repair and greater tuberoplasty may offer a promising and safe method for treating massive rotator cuff tears when the supraspinatus and infraspinatus tendons are irreparable. Workers' compensation claim may predict lower outcome scores.