This study was designed to compare the analgesic effects of intravenous Nalbuphine 0.2mg/kg with intravenous tramadol 1mg/kg in the post-operative period as bolus dose, keeping in account the onset of action, duration of analgesia, hemodynamic changes and side effects like respiratory depression, nausea, vomiting, pruritis and sedation. Eighty patients scheduled for elective surgery under general anaesthesia are randomly selected with forty patients in each group. Randomization was done by block randomization technique. Percentage of pain relief was highly significant (p<0.001) mean VAS score 0.72±0.64 in nalbuphine group as compared with mean VAS score 1.72±0.75 in tramadol group at 30 min. Nalbuphine appears to be a safe and effective analgesic for the relief of moderate to severe postoperative pain than tramadol in equianalgesic doses with minimum circulatory effects, providing good sedation and significantly lower incidence of nausea and vomiting.