Delirium is common in intensive care patients. Dexmedetomidine is increasingly used for sedation in this setting, but its effect on delirium remains unclear. The primary aim of this review was to examine whether dexmedetomidine reduces the incidence of delirium and agitation in intensive care patients. We sought randomised clinical trials in MEDLINE, EMBASE, PubMed and CENTRAL from their inception until June 2018. Observational studies, case reports, case series and non-systematic reviews were excluded. Twenty-five trials including 3240 patients were eligible for inclusion in the data synthesis. In the patients who received dexmedetomidine (eight trials, 1425 patients), delirium was reduced, odds ratio (95%CI) 0.36 (0.26-0.51), p