Introduction: The effectiveness of a local anaestheticis increased by the addition of an adjuvant. Magnesium sulphate along with bupivacaine is effective in reducing the pain and extending the analgesia period. Aim: To compare the duration of analgesia among subjects receiving plain bupivacaine and bupivacaine with magnesium sulphate among patients undergoing total abdominal hysterectomy. Materials and Methods: This double-blinded randomised clinical trial was conducted in Department of Anaesthesiology at Shri Sathya Sai Medical College and Research Institute, Ammapettai, Tamil Nadu, India, (tertiary care center) between November 2019 and October 2021. The study was done among 50 subjects undergoing elective total abdominal hysterectomy. The subjects were divided into two groups, one group received only bupivacaine while the other group received bupivacaine with 500 mg magnesium sulphate. Onset and duration of blocks were observed. Haemodynamic parameters were monitored intraoperatively and postoperatively. Data was analysed using Chi-square test, Fischer’s exact test. Results: Demographic variables like age (p-value=0.17), height (p-value=0.62), weight (p-value=0.14) and BMI (p-value=0.24) were comparable between the two groups. The mean duration of analgesia was significantly more among the bupivacaine and magnesium sulphate group (416.72±93.6) in comparison to the bupivacaine alone group (204.56±71.25). The bupivacaine and magnesium sulphate group required two doses of rescue analgesia in 24 hours, while the other group required four doses of analgesia. Significantly more side-effects were noted among the bupivacaine alone group (12 vs 6) (p-value=0.04). Conclusion: The study showed that bupivacaine and magnesium sulphate group showed less intraoperative side effects, reduced postoperative VAS score increased duration of analgesia, decreased requirement of analgesia required in 24 hours and reduced postoperative side-effects.