Hypothermia, a body temperature of <36 °C, has been shown to increase cardiac mortality, the incidence of postoperative infections, and the length of hospitalization following general surgery. However, studies assessing the incidence of hypothermia during primary total hip and total knee arthroplasty (THA and TKA) have not previously been demonstrated. In this prospective observational study, incidence of hypothermia was measured among 672 patients (415 underwent THA and 257 TKA). The incidence of hypothermia for THA and TKA was 26.3 and 28.0%, respectively. In conclusion, over a quarter of patients in this study are exposed to hypothermia. This study highlights the requirement for interventions to prevent peri-operative hypothermia.