Background: Post operative pain relief can be provided by pharmacological and non-pharmacological methods. Magnesium is the fourth most plentiful cation in the body. This study is designed to assess the effectiveness of using intrathecal and epidural magnesium (Mg) in reducing intra and post operative analgesic requirements and to compare the quality of analgesia of intrathecal bupivacaine-fentanyl-magnesium mixture with intrathecal bupivacaine-fentanyl mixture. Material & Methods: A Hospital based prospective single center study done on 30 ASA I & ASA II patients in the age group of 18 years to 65 years admitted undergoing elective orthopaedic lower limb surgeries at government medical college, Amritsar, Punjab, India during one year period. Patients with duration of surgery between 1-2:30 hours were only included in the study. Unanticipated prolonged duration of surgery was excluded from the study. Intra-operatively the patient was monitored with ECG, BP and SpO2. Ramsay sedation scale (RSS) was also noted every 30 min during intraoperative period. Urine output was monitored hourly. Qualitative variables were compared with `Chi-square test’ and quantitative variables were compared with ‘the student ‘t’ test’. The level of statistical significance was set at P < 0.05. Results: The demographic profile was compared and there was no statistical significance in between the groups. Time of first rescue analgesia (hrs.) was 3.16±0.54 in group P and 6.03±0.62 in group M. Which was statistically significant (P<0.001***). Average no. of epidural top up was higher in group P as compared to group M. Conclusion: We concluded thatSingle dose administration of intrathecal and epidural magnesium to intrathecal bupivacaine-fentanyl mixture provides effective postoperative analgesia in patients undergoing elective orthopaedic lower limb surgeries, without any hemodynamic instability.