Background Admission temperature is inversely correlated with mortality and morbidity risk in extremely preterm newborns (EPNs). As almost all EPNs require advanced resuscitation at birth, we improved a simple and comprehensive management protocol to reduce admission hypothermia. This study reports the changes over the past 15 years in the rate of admission hypothermia in all EPNs. It clarified the distribution of admission temperature and the risk factors for developing admission hypothermia in recent EPNs. Methods This single‐center study retrospectively analyzed the EPNs delivered at our institution between January 2006 and December 2020. The comprehensive management protocol, including warming equipment, plastic wrapping, aluminum‐polyethylene sheet, and room temperature, was applied to avoid heat loss during resuscitation. On admission, the rectal temperature was measured and defined as moderate (32.0–35.9 °C) or mild (36.0–36.4 °C) hypothermia. Results Overall (n = 432), the rate of admission with moderate hypothermia decreased from 48% in 2006 to 8% in 2020. In the recent evaluation of 80 EPNs delivered in 2017–2020, 10 (13%) and 26 (33%) had moderate and mild hypothermia on admission, respectively. Extremely preterm newborns with moderate‐to‐mild hypothermia had a significantly smaller gestational age and lower birthweight than those without hypothermia. No significant differences in the other perinatal and environmental risk factors were observed between EPNs with and without hypothermia. Conclusions Our comprehensive management protocol reduced the rate of moderate hypothermia on admission in EPNs to only 13%. However, eliminating mild hypothermia remains a challenge and requires continuous improvement, especially in smaller EPNs.