The reported functional results of rotator cuff repair performed arthroscopically have been good. Only little is known about the cuff integrity after arthroscopic repair and how it influences the outcome. The aim of the study is to set a baseline of what rate of healing response respectively re-tears to expect and how cuff integrity alters the outcome. Fifty-three consecutive patients with an isolated supraspinatus tendon tear were arthroscopically operated and their tendons repaired. All pre- and postoperative data were prospectively collected. At a minimum follow-up after 24 months (average 26.4 months), the integrity of the cuff was evaluated by an open magnetic resonance imaging and the patients' function and satisfaction were documented and graded to the sex- and age-related Constant-score also using a dynamometer for strength testing. The re-tear rate was 24.5% with 13 non-healed tendons. The Constant-score of all patients improved significantly. The scores of the patients with a re-tear were significantly lower than those of the patient with an intact cuff. That was due to a less good performance in strength testing. The other categories of the Constant-score did not show any differences. The age of the patients with a re-tear was significantly higher. With the exception of age, we did not find any negative prognostic factor for a re-tear, and with the exception of re-tear no other factor influenced the Constant-score. Arthroscopic supraspinatus tendon repair yields a re-tear rate of 25% which is comparable with the results of open or mini/open repair. Cuff integrity influences postoperative strength and Constant-score. Patients older than 65 years show a higher re-tear rate. Therapeutic Level IV is the level of evidence.