Background: Nalbuphine, a relatively newer mixed agonist–antagonist opioid, has a potential to attenuate the μ- opioid effects and to enhance the κ-opioid effects. Pentazocine is also a mixed agonist-antagonist analgesic with agonistic action at κ and σ recptors and a weak antagonistic action at μ receptor. Aim: This study is designed to quantitatively examine the effects of adding Nalbuphine and Pentazocine to hyperbaric Bupivacaine chloride in spinal anaesthesia, to evaluate the efficacy, to know the duration of pain relief and to know the incidence of adverse effects and complications if any. Methods: 100 patients were selected by randomization and divided into two groups Group A (n=50) = received 0.8 mg (0.5ml) nalbuphine with 15 milligrams (3ml) of 0.5% hyperbaric bupivacaine intrathecally. Group B (n=50) = received 3 mg (0.5ml) of pentazocine with 15 milligrams (3ml) of 0.5% hyperbaric bupivacaine intrathecally. All durations were calculated considering the time of spinal injection as time zero. Assessment of pain intra operatively was done by noting Visual Analogue Scale score hourly.Post-operative pain score (VAS) and sedation score were recorded at 1 hr,2 hr, 3 hr, 4 hr, 5 hr, 6 hrs, 12 hrs, 24 hrs. Conclusion: It was observed that nalbuphine hydrochloride (0.8 mg) when added to intrathecal 0.5 % hyperbaric bupivacaine provided longer duration of sensory blockade, excellent quality, and longer duration of postoperative analgesia with good sedation and minimal side effects.