PurposeThis study was conducted to determine the effect of active warming on intraoperative body temperature and comfort before total knee arthroplasty. DesignThis study was a randomized controlled trial designed according to the Consolidated Standards of Reporting Trials. MethodsThe study was conducted on 54 patients in a public hospital in Türkiye. In the study, patients in the intervention group were prewarmed for 30 minutes before surgery. The patients in the intervention and control groups were warmed with a warming bed during the surgery. FindingsIn this study, the first entry temperature to the operating room after anesthesia induction and the mean body temperature of the patients in the intervention group were higher than the control group. The mean comfort score of the patients in the intervention group was higher than the control group. ConclusionsAs a result of this study, we found that the combination of preoperative prewarming and intraoperative warming reduced the decrease in the patient's body temperature and increased the comfort.