Purpose: Some studies have reported that warmed humidified carbon dioxide (CO 2 ) insufflation in adult laparoscopic surgery could reduce pain and improve the core body temperature (CBT). However, similar studies are lacking in infants. Thus, this study aimed to investigate the clinical effects of warmed, humidified CO 2 insufflation in pediatric patients undergoing major laparoscopic surgeries. Methods: From January 2015 to December 2017, infants who underwent major laparoscopic surgeries in Ningbo Women and Children's Hospital were randomized to Group A (standard CO 2 insufflation) or Group B (warmed humidified CO 2 insufflation, 35°C, 95% relative humidity). Change in CBT at the end of surgery was the primary outcome. Secondary outcomes included surgery time, intraoperative blood loss, oxygen saturation (SO 2 ), and Face, Legs, Activity, Cry and Consolability (FLACC) scale. These variables were compared between the 2 groups. Results: Sixty-three infants (38 females, 25 males) were included; 30 patients were in Group A and 33 in Group B. The diseases treated with the laparoscopic approach included congenital megacolon, congenital diaphragmatic hernia, and intestinal malrotation. No deaths were noted. CBT was significantly higher in Group B at the end of surgery ( P = .021). The occurrence of postoperative shivering ( P = .02), hypothermia ( P = .032), bowel movement ( P = .044), and hospital stay ( P = .038) was significantly different between the 2 groups; Group B had less shivering and hypothermia occurrence after surgery. Moreover, Group B demonstrated a more rapid postoperative recovery of bowel movement and shortened hospital stay than Group A. There was no statistical difference in operative time ( P = .162), intraoperative blood loss ( P = .541), SO 2 ( P = .59), and FLACC scale ( P = .65) between the 2 groups. Conclusion: The use of warmed humidified CO 2 insufflation in infants undergoing major laparoscopic surgery was helpful for maintaining normothermia and was associated with several positive postoperative outcomes, including less shivering and hypothermia, faster recovery of bowel movement, and shortened hospital stay.