Background:The objective of this study was to evaluate and compare the effects of three methods of using intravenous (IV), subcutaneous and intranasal (IN) fentanyl for pain management following general anesthesia in patients undergoing cesarean section.Materials and Methods:A prospective, randomized, single-blind clinical trial was done on 75 patients aged 20–40 years, American Society of Anesthesiology-1, who had a normal singleton pregnancy beyond 36 weeks of gestational age. Patients were randomized to receive 50 μg fentanyl intravenously (Group 1), subcutaneously (Group 2) or intranasally (Group 3) after closure of incision. The pain intensity, nausea, the systolic, and diastolic blood pressures were assessed.Results:All groups were equivalent for baseline characteristics. The average pain visual analog scale (VAS) score was less in the second group who received fentanyl subcutaneously at the time of recovery admission (6.8 ± 1.5) (P = 0.037) and after 3 h (6.36 ± 1.5) (P = 0.033) postoperatively. The mean VAS score of nausea and the mean systolic and diastolic blood pressures were not significantly different between three groups throughout the study (P > 0.05).Conclusion:subcutaneous fentanyl is an effective alternative to IV and IN route of administration for pain management.