404 patients undergoing arthroscopic rotator cuff repair were randomized to receive either a sling or no sling. Outcomes of interest included external rotation (ER) of the shoulder joint, forward flexion angle, the American Shoulder & Elbow Surgeons (ASES) score, Constant Score, and the Single Assessment Numeric Evaluation (SANE) score evaluated at 3 and 6 months, and at last follow-up. At the final follow-up, the no-sling group showed greater external rotation. There were no significant differences in forward flexion angle between the two groups. Short-term follow-up showed no significant differences in ASES, Constant, and SANE scores. The long-term follow-up revealed the sling group had significantly higher ASES and Constant scores, but no significant difference in SANE scores between the two groups.