110 patients with a medium- to large-sized, full-thickness rotator cuff tear, who were scheduled for an arthroscopic single-row repair were randomized to the procedure with or without the use of platelet-rich plasma (PRP). The PRP was prepared institutionally and injected intraoperatively over the repair site. Clinical outcome measures of visual analog scale (VAS) pain, Constant-Murley, University of California-LA, and American Shoulder and Elbow Surgeons (ASES) scores were assessed over a 24-month follow-up. In addition, ultrasonographic evaluation of cuff healing was performed. The PRP group demonstrated significantly better results for VAS pain from 1-6 months, Constant-Murley score from 12-24 months, and UCLA scores from 6-24 months after surgery when compared to the control group. As well, the PRP group demonstrated a significantly lower rate of retear on ultrasound after 24 months when compared to the control group.