Abstract Diabetes mellitus (DM) is a common comorbidity and risk factor for postoperative complications in head and neck (H&N) microsurgical reconstructions. Our study focused on the association between DM and individual complications regarding both surgical and medical aspects. A meta-analysis of English-language articles comparing a series of complications between DM and non-DM H&N free-flap recipients was performed by comprehensive meta-analysis (CMA). Twenty-seven articles presented 14,233 H&N free-flap reconstructions, and a subset of 2329 analyses including diabetic cases was included for final analysis. Total postoperative (RR = 1.194, p