Background The most common complication in the surgery for rotator cuff (RC) tears is postoperative shoulder stiffness. The evidence for the postoperative treatment of this condition is scarce. This study assessed the effects of a postoperative program at the onset of shoulder stiffness following arthroscopic RC repair. Methods A single-group pre- and post-test design was included. Participants performed a 6-week program. Primary outcomes were shoulder and upper limb function assessed with the Constant–Murley and Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaires, respectively. Secondary outcomes included pain intensity at rest and during movement with the visual analog scale (VAS), and shoulder range of motion assessed with a goniometer. Results A total of 115 adult males were included. The intervention produced a positive effect on the Constant–Murley (+35.6 points, p<0.001) and DASH questionnaire (−26.2 points, p = 0.005); VAS at rest (−2.8 cm, p<0.001); VAS at movement (−2.7 cm, p<0.001); and shoulder ROMs.