A wireless and wearable axillary thermometer (iThermonitor) has been validated for perioperative core temperature monitoring in adults. The purpose of this study was to evaluate its accuracy in pediatrics having non−cardiac surgery. Design: Prospective observational study. Methods: From January 2019 to December 2019, 70 children aged younger than 14 years undergoing surgery in a tertiary hospital were selected. Pairs of esophageal temperatures (T Eso ), rectal temperatures (T Rec ), and axillary temperatures monitored by the iThermonitor (T iTh ) were collected every 5 min during surgery. Taking T Eso as reference, the bias between T Eso and T iTh and the proportion of bias within §0.5°C were calculated. Bland-Altman method was used to analyze the 95% of limits of agreement (LOA) between T iTh and T Eso . The same analyses were done for T Rec. Findings: A total of 2232 pairs of temperatures were collected. The bias (mean § SD) between T iTh and T Eso was -0.07°C § 0.25°C, and 95% LOA was -0.07°C § 0.50°C. The proportion of bias within §0.5°C accounted for 96% (95% Confidence Interval [CI], 92-98%). Higher bias and 95% LOA, and lower proportion of bias within § 0.5°C were found between T Rec and T Eso than those between T iTh and T Eso . Conclusion: During pediatric non−cardiac surgery, axillary temperature derived from iThermonitor is in good agreement with esophageal temperature and can be used as an alternative to core temperature.