Background: Postoperative nausea and vomiting (PONV) remains one of the commonest causes of significant morbidity after tonsillectomy in children. A variety of prophylactic anti­emetic interventions have been reported, but there has only been a limited systematic review in this patient group. Aim: To find an efficient antiemetic agent for prevention of PONV in children undergoing tonsillectomy performed under G.A. Methods: We included 75 patients in the age group of 5­15 years undergoing Tonsillectomy. Patients were randomly divided into 3 groups of 25 patients each. The patients of Group I received Metoclopramide 0.25mg/kg, Group II Ondansetron 100 mcg/ kg and group III received Granisetron 40 mcg/kg intravenously just prior to induction of anesthesia. The following parameters were monitored during the study: Duration and quality of antiemesis, Pulse rate, Blood pressure, Modified Aldrete’s Score and Side effects if any. Results: Based on scoring system, it was found that the recovery score was 9. The patients were observed from 0–3 hrs and 3­24 hrs following Tonsillectomy for episodes of Nausea and / or Vomiting. Incidence of nausea and/or vomiting during 3­24 hrs after surgery is 44%, 20% and 8% in Groups I, II, and III respectively , with a statistically significant difference between Metoclopramide (Gr. I) and Granisetron (Gr. II ). Conclusion: Granisetron in a dose of 40 mcg/kg is more effective with very less side effects than Metoclopramide and Ondansetron in the long term prevention of PONV in the children undergoing tonsillectomy under GA.