Purpose: It is well documented that patients with severe burns are at increased risk of developing hypothermia. However, the time in hypothermia of severe burn patients and the impact of temperature management practices during resuscitation of patients is poorly characterised. This study aimed to investigate factors associated with time in hypothermia of severe burn patients during the first 24-hour resuscitation period and the relationship of time in hypothermia with hospital mortality. Methodology: A 5-year retrospective cohort study was conducted of adult patients (>18 years of age) with severe burns (>20% total body surface area, TBSA) admitted to a burns service hospital. Data was extracted using the Burns Registry of Australia and New Zealand and supplemented with electronic medical records. Hypothermia was defined as a body temperature <36.0°C. Variables investigated included patient demographics, injury characteristics, surgery within 24 hours, frequency of temperature recordings and use of warming devices. Results: 142 patients were eligible and included in analysis. In the first 24 hours since presentation to hospital, 108 patients developed hypothermia and the median time in hypothermia was 315.5 minutes (IQR 23-559). Patients who experienced a longer time in hypothermia were associated with a higher TBSA% burnt (p < 0.001), inhalation injury (p < 0.001), non-accidental intent (p = 0.019), use of forced-air warming blankets (p = 0.021) and infusion of warmed fluids (p = 0.025). Time in hypothermia was significantly associated with hospital mortality (OR 1.002; 95%CI:1.001-1.004; p < 0.001). Conclusion: Hypothermia was commonly observed among patients with severe burns and significantly associated with hospital mortality. Frequent observations of temperature and use of warming devices were not associated with lower time in hypothermia, although use was most likely reactive. Protocolised monitoring of temperature and warming strategies is indicated.