Purpose: The aim of this study was to compare the effects of intrathecal fentanyl and intrathecal morphine combined with spinal anesthesia on postoperative pain control for inguinal hernia repair.Materials and Methods: Fifty patients aged 18-60 years with American Society of Anesthesiologists physical status I-II scheduled for elective inguinal hernia repair surgery were enrolled in this prospective randomized double-blinded study. Patients received spinal anesthesia with either 25 mcg fentanyl plus 12.5 mg heavy bupivacaine intrathecally (group F, n=25) or 0.1 mg morphine plus 12.5 mg heavy bupivacaine intrathecally (group M, n=25).Hemodynamic parameters, time to first analgesic requirement, postoperative pain scores, the number of analgesic requirements and side effects over postoperative 24 h were recorded.Results: Pain scores were significantly lower in group M compared with group F in the postoperative 24 h. The time to first analgesic requirement was higher in group M than group F. Analgesic requirement was higher in group F than group M for postoperative 24 h. Conclusion: We concluded that the addition of 0.1 mg morphine intrathecally to 12.5 mg heavy bupivacaine provides improved postoperative analgesia, especially after postoperative 12 h than 25 mcg fentanyl for inguinal hernia repair under spinal anesthesia.