OBJECTIVE: Acute kidney injury (AKI) is a common complication after cardiac surgery, and there is no pharmacologic prophylaxis of AKI. Some animal and clinical studies showed the renoprotection effect of dexmedetomidine (DEX) on AKI, but data from other trials came to the opposite conclusion following cardiac surgery. METHODS: We searched databases including EMBASE, PubMed, and Cochrane CENTRAL for randomized controlled trials (RCTs) focused on DEX for AKI in adult patients after cardiac surgery. The primary outcome was incidence of AKI. Secondary outcomes were mechanical ventilation (MV) duration, intensive care unit (ICU) length of stay (LOS), hospital LOS and mortality. RESULTS: Fifteen trials enrolling 2907 study patients were collected in the meta-analyses. Compared with controls, DEX reduced the incidence of postoperative AKI [odds ratio (OR), 0.66; 95%confidence interval (CI), 0.48-0.91; P=0.01], and there was no significant difference between groups in postoperative mortality (OR, 0.63; 95%CI, 0.32-1.26; P=0.19), MV duration [weighted mean difference(WMD), -0.44; 95%CI, -1.50-0.63; P=0.42], ICU LOS (WMD, -1.19; 95%CI, -2.89-0.51; P=0.17) and hospital LOS (WMD, -0.31; 95%CI, -0.76-0.15; P=0.19). CONCLUSIONS: Perioperative DEX use reduced the incidence of postoperative AKI in adult patients undergoing cardiac surgery. No significant decrease existed in mortality, MV duration, ICU LOS and hospital LOS owing to the DEX administration.