Background and Aims:Postoperative nausea and vomiting (PONV), one of the common complications following strabismus surgery, would delay the ambulatory discharge time. The aim of this retrospective study was to determine the risk factors of PONV in patients undergoing ambulatory strabismus surgery under general anaesthesia, with the treatments of dexamethasone and 5-HT3 antagonist combination.Methods:We reviewed 721 consecutive patients (12–60 years old) undergoing ambulatory strabismus surgery under general anaesthesia at an academic eye centre between December 2016 and January 2019. Patients received prophylactic treatment of dexamethasone and 5-HT3 antagonist combination during anaesthesia induction, and PONV was evaluated during the early recovery period before discharge.Results:The dexamethasone and 5-HT3 antagonist combination effectively reduced the incidence of PONV (3.05%, 22/721), and the patients who experienced PONV had statistically prolonged phase II recovery time as compared those who did not (P = 0.006). The sum of the extraocular muscles manipulated and the use of nalbuphine (vs flurbiprofen axetil) were the independent risk factors for PONV (P < 0.05).Conclusion:The sum of the extraocular muscles manipulated and the use of nalbuphine are potentially modifiable risk factors for PONV after strabismus surgery with the treatments of dexamethasone and 5-HT3 antagonist combination.