Background: Although many studies are available in the literature that has analyzed the effects of morphine, nalbuphine, and other opioids, no study had compared the effects of nalbuphine versus morphine as an adjuvant to bupivacaine in the supraclavicular block under the guidance of ultrasound. Methodology: A randomized, double-blinded, prospective study was carried out on 60 patients of the American Society of Anesthesiologists Class I and II who were undergoing upper limb surgeries under the supraclavicular block. Patients were randomly allocated into two groups ( n = 30). Group N received 20 ml of 0.5% bupivacaine with 50 μg.kg −1 of nalbuphine, while Group M received 20 ml of 0.5% bupivacaine with 50 μg.kg −1 of morphine. The characteristics of sensory and motor blocks, hemodynamic changes, duration of analgesia, adverse effects, and analgesic requirements were studied at different time intervals. Results: In Group N, there was a statistically significant reduction in the time of onset of sensory block (9.9 ± 3.0 vs. 12.2 ± 2.6 min, P = 0.002) and motor block (14.4 ± 3.6 vs. 19.4 ± 3.6 min, P = 0.0005). The duration of sensory and motor blockade and duration of analgesia were comparable. There was no statistically significant difference regarding block characteristics and hemodynamic parameters. Conclusion: Nalbuphine when added to bupivacaine as an adjuvant had significantly shortened the time of onset of sensory and motor blockade than morphine. However, the duration of analgesia, sensory and motor blockade of nalbuphine versus morphine were comparable.