Prevention and treatment of hypothermia by active warming in perioperative period care is recommended but scientific evidence of its effectiveness in a clinical setting is scarce. The purpose of this study was to determine the effects of warmed intravenous fluids (WIVF) on the core body temperature and the patients' thermal comfort. Baseline data of 105 male patients undergoing TUR-P surgery and bladder irrigation were analyzed. The experimental group was warmed using active WIVF, and the control group's routine care was conducted using a cotton blanket. Body temperature was higher in patients in the experimental group than those in the control group. Repeated measures Manova revealed significantly different core temperature changes between groups (F = 34.446, p = .001). The thermal comfort scores were also higher in the experimental group than in the control group (x(2) = 203.552, p = .001). The findings indicated that WIVF can enhance body temperature and improve the thermal comfort of patients.