Context:Subarachnoid block or spinal anesthesia is a commonly used technique for lower abdominal and lower limb surgeries. Bupivacaine is the commonly used cost-effective drug which gives satisfactory analgesia for 90–120 min. Additives such as opioids and α2 agonists extend the analgesia in the postoperative period. In this study, we compared the effects of nalbuphine with fentanyl.Aims:The aim of this study is to compare the effects of intrathecal nalbuphine and fentanyl as adjuvants to hyperbaric bupivacaine in regard to time of onset of sensory blockade, duration of sensory blockade, two-segment sensory regression time, duration of effective postoperative analgesia, and incidence of side effects.Settings and Design:This was a prospective, randomized double-blind study.Subjects and Methods:After ethical committee permission and patient consent, 124 patients aged 18–55 years with American Society of Anesthesiologists physical status I and II were randomly divided into two groups – Group N: hyperbaric bupivacaine with nalbuphine (300 μg); Group C: hyperbaric bupivacaine with fentanyl (25 μg).Results:Duration of onset of sensory blockade was 3.9 ± 0.35 min in Group C and 3.1 ± 0.18 min in Group F. Two-segment sensory regression time was prolonged in Group C (193.16 ± 39.55) compared to Group F (167.41 ± 30.17 min).Conclusions:Intrathecal nalbuphine at a dose of 300 μg in 3 ml 0.5% heavy bupivacaine in patients undergoing elective lower abdominal surgeries showed delay in onset time for sensory blockade and produced prolonged postoperative analgesia, prolonged sensory blockade, and minimal bradycardia which could be easily managed.