Background: Postoperative shivering is a frequent complication in recovery room after general anesthesia and has been reported in 40-70% of patients undergoing surgery. Postoperative shivering might cause hypoxemia, increase in oxygen consumption, a linear increase in carbon dioxide production, lactic acidosis, and increased intraocular pressure and intracranial pressure. The aim of this study was to compare the effects of different doses of granisetron on preventing postoperative shivering in patients undergoing septorhinoplasty under general anesthesia. Methods: 90 patients aged 18-60 years old with grades Ι or ΙΙ of American Society of Anesthesiologists (ASA) physicals classification were allocated to the study. The first group (G1) received Granisetron 1mg Intra Venous (IV) before anesthesia induction; the second group (G2) received 3mg Granisetron IV before anesthesia induction and the last group, the control group, received Normal Saline (NS). Three groups were matched regarding age, gender, weight and duration of surgery. Shivering grade and time of operation were recorded in the recovery room. Results: 90 patients scheduled for septorhinoplasty, including 54 men and 36 women, were enrolled to the study.  The mean age of the patients was 28.53 ± 8.62 (18-60) years. The number of the patients suffering from shivering in the recovery room was significantly less in group G2 rather than control group (P=0.006) and also need to therapy was significantly less in this group (G2) compared with the control group (P=0.002).  Conclusion: Prophylactic use of granisetron (3mg, IV) can be effective in preventing postoperative shivering following septorhinoplasty.