Purpose: We assessed long-term outcomes in acutely admitted adult patients with delirium treated in intensive care unit (ICU) with haloperidol versus placebo. Methods: We conducted pre-planned analyses of 1-year outcomes in the Agents Intervening against Delirium in the ICU (AID-ICU) trial, including mortality and health-related quality of life (HRQoL) assessed by Euroqol (EQ) 5-dimension 5-level questionnaire (EQ-5D-5L) index values and EQ visual analogue scale (EQ VAS) (deceased patients were assigned the numeric value zero). Outcomes were analysed using logistic and linear regressions with bootstrapping and G-computation, all with adjustment for the stratification variables (site and delirium motor subtype) and multiple imputations for missing HRQoL values. Results: At 1-year follow-up, we obtained vital status for 96.2% and HRQoL data for 83.3% of the 1000 randomised patients. One-year mortality was 224/501 (44.7%) in the haloperidol group versus 251/486 (51.6%) in the placebo group, with an adjusted absolute risk difference of − 6.4%-points (95% confidence interval [CI] − 12.8%-points to − 0.2%-points; P = 0.045). These results were largely consistent across the secondary analyses. For HRQoL, the adjusted mean differences were 0.04 (95% CI − 0.03 to 0.11; P = 0.091) for EQ-5D-5L-5L index values, and 3.3 (95% CI − 9.3 to 17.5; P = 0.142) for EQ VAS. Conclusions: In acutely admitted adult ICU patients with delirium, haloperidol treatment reduced mortality at 1-year follow-up, but did not statistically significantly improve HRQoL.