Introduction: Perioperative hypothermia (POH) emerges as an important problem in increasing the morbidity and mortality rates of geriatric patients. The purpose of this study was to determine the incidence of POH in geriatric patients undergoing elective surgery. In addition, to determine the risk factors associated with POH in geriatric patients, to contribute to the improvement of temperature monitoring awareness and body temperatures. Methods: Patients over 65 years of age who would undergo elective surgery under sedoanalgesia, general and regional anesthesia were included in the study. Demographic and operative data of the patients, body temperatures at the time of entering the waiting room and exiting the waiting room in the pre-operative period, at the 0th min (min), 60th min, 120th min, 180th min, and 240th min in the intraoperative period and in the post-operative period, and body temperatures at the time of entry and exit from the recovery unit were measured from the tympanic membrane and recorded. Body temperatures below 36°C were accepted as hypothermia. Results: A total of 178 patients, including 75 females (42.1%) and 103 males (57.8%), were included in the study. The mean age of the patients was 73±7.44 years. While the pre-operative mean body temperature of the patients was 36.8±0.46°C, the mean body temperature at the entrance and exit of the postoperative recovery unit was 35.61±0.89°C and 36.11±0.63°C, respectively. In the intraoperative period, the mean value of body temperature at the 0th min was found to be higher than the 60th, 120th, and 180th min, which was statistically significant (p<0.01). A statistically significant difference was found in all time frame comparisons of prolonged operation time and decrease in body temperature (p<0.01). Discussion and Conclusion: In our study, POH emerges as an important problem in geriatric patients. We suggest that routine monitoring of body temperature and warming of patients are necessary to prevent hypothermia in geriatric patients. Especially in operations that are planned to take a long time; improvements should be implemented quickly to avoid hypothermia.