Clinical outcomes after rotator cuff repair associated with diabetes mellitus(DM) are generally favorable, but no study has attempted to establish the influence of DM on outcomes after rotator cuff repair. To conduct a meta-analysis of clinical studies evaluating patient outcomes between people with DM and people without DM after rotator cuff repair. Meta-analysis. A literature search of the Embase, PubMed, and Cochrane Library databases was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Cohort studies and case-control studies about clinical outcomes after rotator cuff repair comparing people with DM and people without DM were included. Statistical analysis was performed with RevMan (v 5.3.3). Nine clinical studies that met the inclusion criteria were identified and included a total of 314 patients treated with DM and 1092 patients without DM. The failure rate was significantly higher in the DM group than in Non-DM group (23.97% compared with 16.60%, OR: 2.39; 95% CI, 1.69-3.37; p < 0.001). The postoperative retear rate and showed a significant difference between the two groups (24.5% and 13.7%; OR: 2.41; 95% CI, 1.57-3.71; p<0.001). The DM group showed a higher rate of postoperative unhealed cuff than the Non-DM group(41.81% and 25.23%; OR: 2.14; 95% CI, 1.69-3.37; p=0.01).Postoperative Range of motion(ROM) at 12 months after surgery show a significant difference in the range of external rotation between two groups (WMD: -6.02; 95% CI, -7.54 to -4.50; p<0.001).The preoperative Japanese Orthopaedic Association (JOA) score, the comparison of pre- and post-operative JOA scores showed a significant difference in the DM and Non-DM group(p<0.001). The postoperative JOA score, the pre- and post-operative muscle strength, the pre- and postoperative visual analog scale (VAS) show significant difference between the the DM and Non-DM group(p<0.001). The postoperative infection rates, the rates of postoperative shoulder stiffness, the preoperative ROM, the postoperative ROM at 6 months, the postoperative ROM at 12 months of forward flexion and abduction, the American Shoulder and Elbow Surgeons score, the University of California, Los Angeles scores, and the preoperative Constant-Murley scores show no significant difference between the two groups. This meta-analysis indicates that DM may be relative to a higher rate of shoulder retear and cuff unhealing. However, patients with DM can achieve great clinical outcomes after cuff repair, compared to patients without DM. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.