Background: Nalbuphine is a synthetic opioid. It has mixed agonist-antagonist action. When used as an adjuvant to intrathecal bupivacaine it acts on kappa receptors in the dorsal horn of the spinal cord producing analgesia. We aimed the present study to evaluate the effectiveness of intrathecal nalbuphine as an adjuvant. At the same time, the efficacy of nalbuphine for sensorimotor characteristics and postoperative analgesia was also judged. Method: A total of 100 patients were enrolled. They were randomly allocated into two equal groups. Group B: received 15 mg hyperbaric bupivacaine (3ml) 0.5% + 0.5ml normal saline and Group BN: received 15 mg hyperbaric bupivacaine (3ml) 0.5% + Inj. Nalbuphine 500__ampersandsignmu;g (0.5ml). The sensorimotor characteristics, duration of effective analgesia, any hemodynamic alterations, and side effects were noted. Results: The sensory and motor block characteristics were significantly faster in group BN than group B. The duration of sensory and motor block, as well as duration of effective analgesia, was significantly prolonged in group BN in comparison with group B. Quality of analgesia during the procedure was excellent in 90% and 94% in group B and BN, respectively. Sedation score, hemodynamic parameters, and respiratory rate changes were comparable between both groups. In group B, 4% patient complained of nausea/vomiting, intraoperative hypotension noted in 4% and post-dural puncture headache was recorded in 1 patient while in group BN bradycardia was observed in 3 patients. Conclusion: Addition of 500__ampersandsignmu;g of nalbuphine as an adjuvant to hyperbaric bupivacaine 0.5% for spinal anaesthesia provides excellent analgesia with a longer duration of effective analgesia in comparison to intrathecal hyperbaric bupivacaine 0.5% alone.