Rotator cuff tear and glenohumeral osteoarthritis are 2 common diseases, but there are few studies about their clinical correlation. The purpose of this study was to evaluate the influence of mild glenohumeral osteoarthritis on the clinical outcome after large to massive rotator cuff repair. This study included 146 patients who underwent rotator cuff repair for large to massive tears and were available for follow-up at a minimum of 2 years. Of the patients, 74 had mild glenohumeral osteoarthritis (group A) and 72 did not have glenohumeral osteoarthritis (group B). The mean visual analog scale score during motion, mean University of California at Los Angeles score, and mean Constant score were 1.8, 30.2, and 87.4, respectively, in group A and 2.0, 30.8, and 89.2, respectively, in group B at final follow-up. The retear rates were 31.1% (23 of 74 patients) in group A and 25.0% (18 of 72 patients) in group B. The osteoarthritis progression rates were 12.1% (9 of 74) in group A and 13.8% (10 of 72) in group B. However, in group A, the osteoarthritis progression rates were 26.1% (6 of 23) for retear cases and 5.9% (3 of 51) for healed cases. There was a significant difference in the progression rates between retear and healed cases in group A (odds ratio, 5.65; P = .022). There were no significant differences in clinical outcomes between patients with and without glenohumeral osteoarthritis before surgery and during final follow-up. The progression of osteoarthritis in large to massive rotator cuff tears is relatively low. However, it is significantly higher in patients with retears in whom osteoarthritis is present.