Aims Large population-based studies have demonstrated increased prevalence of rotator cuff disease amongst diabetics. Recent studies have suggested comparable clinical outcomes from rotator cuff repair despite suggestions of increased complication rates amongst diabetics. However, there is a relative paucity of studies considering the effect of diabetes upon complication rate. We aim to report and quantify the effect of diabetes on complication rates following arthroscopic rotator cuff repair. Materials and methods A retrospective review of a consecutive series of patients undergoing arthroscopic rotator cuff repair between January 2011 and December 2014 was performed. Diabetic status and complication data defined as infection, frozen shoulder, re-tear or re-operation were collected and interrogated. Results A total of 462 patients were included at median follow-up of 5.6 years. Diabetics were significantly more likely to experience frozen shoulder (15.8% vs. 4.4%, p = 0.001), re-tear (26.3% vs. 15.6%, p = 0.042) or at least one complication following surgery (35.1% vs. 22.7%, p = 0.041) compared to non-diabetics. These equated to odds ratios of 4.03, 1.94 and 1.84, respectively. Conclusions Diabetic patients are almost twice as likely to experience complications following arthroscopic rotator cuff repair, including double the risk of repair failure and more than four times the risk of frozen shoulder.