We aimed to evaluate the effect of a single dose of preoperative dexamethasone on postoperative nausea and vomiting (PONV), a frequent complication and a major cause of delayed recovery in pediatric upper gastrointestinal endoscopy (UGIE) under sedation.In this double-blind randomized controlled study, 98 children aged 2 to 14, with American Society of Anesthesiologists status I to II, and undergoing elective UGIE with deep sedation were included and randomly assigned to 2 groups. Preoperatively, after anesthesia induction with sodium thiopental and maintenance with sevoflurane, patients in the intervention (n = 49) and control (n = 49) groups, respectively received 0.1 mg/kg i.v. dexamethasone and 2 cm i.v. 0.9% saline. Postoperatively, PONV incidence was measured as the primary outcome.PONV incidence was significantly less in dexamethasone group (8.2%) compared to the control group (26.5%) (difference = 18.3%, 95% confidence interval: 3.4%-33%, P = 0.016). For secondary outcomes, between-group differences were not statistically significant: incidence of bronchospasm or laryngospasm (both 4.1%, P = 1); emergence delirium assessed with Pediatric Anesthesia Emergence Delirium scale (5.9 ± 3.4 vs 5.7 ± 3.2, P = 0.751); Modified Aldrete score at 0 minutes (9.4 ± 0.8 vs 9.3 ± 0.9, P = 0.909) and at 5 minutes (9.5 ± 0.7 vs 9.4 ± 0.9, P = 0.527); and recovery time (21.1 ± 6.6 vs 23.4 ± 8.6 minutes, P = 0.130).A single preoperative dose of i.v. dexamethasone reduces PONV in children undergoing elective UGIE with deep sedation, but has no significant effect on the patient recovery time or the incidence of postoperative bronchospasm or laryngospasm and emergence delirium.