AIM: To observe the effects of single-dose of fentanyl on sedation and agitation during recovery after pediatric adenotonsillectomy day surgery during anesthesia induction. METHODS: A total of 157 children undergoing elective adenotonsillectomy, with ASA physical status I or II, aged 3-10 years were selected during January and March in 2022 in the Second Affiliated Hospital of Wenzhou Medical University. The children were divided into two groups according to random number table method: remifentanil combined with fentanyl group (group RF, n=78) and remifentanil group (group R, n=79). Children in group RF received a single-dose injection of 1 μg/kg of fentanyl and 2.5 μg/kg of remifentanil during induction, children in group R received an equal volume of normal saline and 2.5 μg/kg of remifentanil injection. Children in both groups were intubated after propofol induction and anesthetized with combination of sevoflurane-remifentanil. The incidence and severity of emergence agitation (EA), Ramsay sedation score and FLACC pain score in post-anesthesia care unit (PACU), extubation time, recovery time, PACU stay time, discharge time were recorded. RESULTS: Compared with group R, the incidence of EA was significantly lower (38.0% vs. 18.0%, P=0.005), the maximum PAED score during recovery was significantly lower (7.7±3.3 vs. 8.9±3.4, P=0.027), and the Ramsay sedation score was significantly higher at 15 min after admission of PACU (4.4±1.1 vs. 3.8±1.4, P=0.01), as well as discharge of PACU (2.0±0.3 vs. 1.8±0.4, P=0.03) in RF group . There was no significant difference in extubation time, recovery time, PACU stay time, discharge time, pain score (discharge of PACU and 2 h after operation) between two groups (P>0.05). CONCLUSION: A single-dose injection of fentanyl (1 μg/kg) during anesthesia induction can increase the degree of sedation and reduce the incidence of EA in PACU after pediatric daytime adenotonsillectomy.