Objectives: To compare time to incidence, extent of incidence and severity of heel pressure injury with a heel off-loading boot (intervention) or pillows (control). Research methodology/design: Multi-centre, single-blinded randomised controlled trial of 394 critically ill patients. Patients were randomised to the intervention or control for heel offloading. Setting: Three hospital intensive care units; two in greater Sydney, Australia and one in regional New South Wales, Australia. Main outcome measures: Time to intensive care unit-acquired pressure injury in heels of patients without pre-existing heel pressure injury within 28 days from intensive care unit admission. Secondary outcomes: incidence of heel pressure injury within 28 days of intensive care unit admission; severity of intensive care unit-acquired heel pressure injuries; occurrence of plantar contractures (a change in ankle dorsiflexion of 5° or greater) within 28 days of admission. Results: Within 28 days of admission, one pressure injury was recorded in the intervention group and 11 in the control group. Hazard of pressure injury incidence within 28 days of admission was significantly lower (p = 0.0239) in heels assigned to the intervention (hazard ratio 0.0896 [95% CI 0.0110, 0.727]). Odds of pressure injury incidence within 28 days of admission were significantly lower (p = 0.0261) in the intervention group (odds ratio 0.0883 [95% CI 0.0104, 0.749]). The pressure injury recorded in the intervention group was superficial (stage 1) whereas those recorded in the control group were more severe (stage 2 to 4). Conclusion: The heel-offloading boot used in this study significantly reduced heel pressure injury occurrence compared with heel offloading using pillows.