Delirium is the most common mental disturbance in critically-ill patients and results in significant morbidity and mortality. Haloperidol is a preferred agent for the treatment of delirium in this population because of its rapid onset of action and lack of hemodynamic effects. Despite its widespread use in the critical care setting, most of the relevant data are obtained from case series or extrapolated from non-critically-ill populations. This review provides an overview of haloperidol pharmacokinetics and a comprehensive summary of the evidence for various haloperidol dosing regimens in the treatment of delirium in critically-ill patients. A comprehensive literature search was conducted in Medline, Embase, and International Pharmaceutical Abstracts with "haloperidol", "delirium", "agitation", "critically-ill", and "intensive care" as keywords. Studies involving haloperidol for delirium prophylaxis, non-critical care settings, and terminally-ill subjects were excluded. Eleven studies were identified: four with intermittent IV haloperidol, four with continuous IV infusion haloperidol, two with oral/enteral haloperidol, and one with IM haloperidol. All of the case reports, case series, and descriptive studies have shown a benefit with haloperidol, but publication bias is likely present. Only three studies were controlled studies, but all had small sample sizes and methodological flaws. Randomized, double-blind, active-comparator trials of haloperidol with allocation concealment are needed. Subsequent research should focus on using validated delirium screening and assessment scales for more objective identification and measurement of delirium outcomes.