Background: Postoperative pain may be a significant reason for delayed discharge from hospital, increased morbidity and reduced patient satisfaction. Nowadays opioids are the mainstay in the treatment of acute postoperative pain. Pethidine is an opioid.But opioids produce side effects like nausea, vomiting, sedation, pruritis, respiratory depression. Diclofenac is a non-selective NSAIDs with good tissue permeability. NSAIDs are particularly Effectiveincasesofsomaticinflammatorypain. Objectives: We conducted this study to compare the efficacy of Injection pethidine and Injection diclofenac as an analgesic for post-operative patients undergoing Hysterectomy. Methods: This was an open-label prospective study that included 60 female patients undergoing lower limb orthopedic surgeries aged 20 years and above. Randomly allocated 30 patients were given Pethidine 50 mg IM three times a day and the rest 30 patients were given Diclofenac 75mg IV two times a day. Post-operative pain scores were recorded using the Visual Analog Scale (VAS) at 6,12,24and 48 hrs. Statistical analysis was done using unpaired t-test. Results: The mean pain score was found less in the diclofenac group compared to the pethidine group at all intervals by VAS (p<0.05). Nausea and dizziness were more commonly reportedinthepethidinegroup. Conclusion: Diclofenac provides effective and better analgesia in acute post-lowerlimb orthopedic surgery pain than pethidine with fewer adverse effects.