Purpose: The purpose of this study was to compare the effectiveness for infants of antifebrile therapy using a hypothermia blanket or rectal antipyretics following open heart surgery. Methods: This was a retrospective study and 174 infants who had open heart surgery at P University Hospital, and whose body temperature body temperature exceeded $37.2^{circ}C$ were included in the study. The assessment tool was composed of 32 items was used for assessment of fever therapy, physiological indexes and antifebrile duration. Physiological indexes included systolic blood pressure, diastolic blood pressure, heart rate, pH, $PaCO_2$, $PaO_2$, $HCO_3{^-}$, $SaO_2$, and $K^+$ and the antifebrile duration was minutes from having a fever until BT returned to normal levels. Results: The antifebrile duration with the hypothermia blanket was shorter than with rectal antipyretics. There were significant differences in the physiological indexes with either type of antifebrile therapy, but drop in BT was greater with the hypothermia blanket than rectal antipyretics. Conclusion: The results of this study indicate that a hypothermia blanket is a non-invasive, non-drug and safe antifebrile therapy. Therefore, a hypothermia blanket can be applied to infants with a fever following open heart surgery.