Background: one of the primary aims of anesthesia is to alleviate the patient's pain and agony, by permitting the performance of surgical procedures without any discomfort. Relief of postoperative pain has gained real importance in recent years considering the central, peripheral and immunological stress response to tissue injury. Any expertise acquired in this field should be extended into the postoperative period, which is the period of severe, intolerable pain requiring attention. So there is a need for extended analgesia without any side effects to achieve this goal. The use of opioids in intrathecal or epidural anesthesia has become popular to optimize postoperative analgesia. However, opioid-induced side effects, such as respiratory depression, nausea, vomiting, urinary retention and pruritus, limit their use. Aim of the Work: the purpose of this study was to assess the postoperative analgesic requirements and the spinally mediated analgesic effects of intrathecal nalbuphine as an adjunct to intrathecal bupivacaine after cesarean section in comparison to intrathecal bupivacaine plus fentanyl. Patients and Methods: eighty female patients came to Demerdash Hospital for cesarean delivery, they were randomly allocated into two equal groups (40 patients) group F and group N. Group F: Bupivacaine-Fentanyl: Patients received an intrathecal injection of 2 ml of 0.5% heavy (hyperbaric) bupivacaine plus 0.5 ml (25 µg) fentanyl. Group N: Bupivacaine-Nalbuphine: Patients received an intrathecal injection of 2 ml of 0.5% heavy (hyperbaric) bupivacaine plus 0.5 ml (0.8 mg) Nalbuphine. Results: the addition of a small dose of nalbuphine or fentanyl to bupivacaine in spinal anesthesia moderately prolonged the time of postoperative analgesia, while the duration of analgesia was more prolonged and the adverse effects were minimal with the group of nalbuphine, our result shows no significant difference, but shows significant difference in the More rapid onset of sensory block with Fentanyl than with Naluphine, more rapid Regression time to S1 dermatome with Fentanyl than with Naluphine, the duration of motor block is shorter with Fentanyl than with Naluphine, patients receive rescue analgesia 6 h postoperatively is fewer with Nalpuphine than Fentanyl. Conclusion: more rapid onset of motor block in fentanyl group than in nalbuphine group, more rapid onset of sensory block with Fentanyl than with Naluphine, more rapid regression time to S1 dermatome with Fentanyl than with Naluphine.