Purpose <p>The aim of this study was to analyze the functional and radiological outcomes of delay arthroscopic repair of traumatic massive rotator cuff tears (mRCTs).</p> Methods <p>This is a prospective study of patients with traumatic mRCTs treated by arthroscopic repair within the first 12&#xa0;months after trauma. Degenerative tears, single tendon tears, associated fractures, severe arthropathy, irreparable tears, patients older than 75, and those with less than 1&#xa0;year of follow-up were excluded. Range of motion, pain, and the ASES score were analyzed. MRI was performed preoperatively to assess the rotator cuff tear and 6&#xa0;months after surgery to evaluate tendon healing. The average follow-up was 22 (± 6.3) months. A <i>p</i> value of &lt; 0.05 was considered statistically significant.</p> Results <p>A total of 20 patients were included, with a mean age of 61.7 (± 8) years, 60% male, 65% dominant side affected, and 65% manual workers. The mean time to diagnosis was 4.5 (± 2.7) months, and the mean time to surgery was 7.6 (± 3) months. The mean ASES score was 80.6 ± 15 95% of patients achieved satisfactory results. Elevation improved by a mean difference of −&#xa0;38 degrees (<i>p</i> &lt; 0.001), external rotation −&#xa0;29 degrees (<i>p</i> &lt; 0.001), pain decreased by 6 points (<i>p</i> &lt; 0.001), and the ASES score improved by 41 points (<i>p</i> &lt; 0.001). The rate of retear was 60% and patients in whom surgery was performed more than 6&#xa0;months after the trauma had a 4.7-fold increased risk of retear (<i>p</i> = 0.018). Patients without a retear demonstrated better postoperative external rotation (<i>p</i> = 0.013) and ASES scores (<i>p</i> = 0.033).</p> Conclusions <p>Delayed arthroscopic repair of massive traumatic rotator cuff tears led to good functional outcomes in 95% of patients, despite a rate of retear of 60%. Patients operated on more than 6&#xa0;months after trauma had a relative risk of 4.7 for presenting a retear.</p>