Introduction: Prescribing practice in hospice/palliative care is largely extrapolated from other areas of clinical practice, with few studies of net medication effects (benefits and harms) in hospice/palliative care to guide prescribing decisions. Hospice/palliative care patients differ in multiple ways from better studied participant groups, hence the applicability of studies in other participant groups is uncertain. Haloperidol, a butyrophenone derivative and dopamine antagonist, is commonly prescribed for nausea, vomiting, and delirium in hospice/palliative care. Its frequent use in delirium occurs despite little evidence of the effect of antipsychotics on the untreated course of delirium. The aim of this study was to examine the immediate and short-term clinical benefits and harms of haloperidol for delirium in hospice/palliative care patients. Method: A consecutive cohort of participants from 14 centers across four countries who had haloperidol commenced for delirium were recruited. Data were collected at three time points: baseline, 48 hours (clinical benefits), and day 10 (clinical harms). Investigators were also able to report clinical harms at any time up to 14 days after it was commenced. Results: Of the 119 participants included, the average dose was 2.1 mg per 24 hours; 42 of 106 (35.2%) reported benefit at 48 hours. Harm was reported in 14 of 119 (12%) at 10 days, the most frequent being somnolence (n=11) and urinary retention (n=6). Seven participants had their medication ceased due to harms (2 for somnolence and 2 for rigidity). Approximately half (55/119) were still being treated with haloperidol after 10 days. Conclusion: Overall, 1 in 3 participants gained net clinical benefit at 10 days.