Background: Pain after thoracotomy is probably the most severe pain experienced by the patient and opioid are one of the most commonly used analgesics for postoperative pain. Hence, the present study was undertaken to compare the efficacy and safety of 25 mcg/hour of fentanyl patch with 20 mcg/hour of buprenorphine patch for postoperative pain management in postthoracotomy patients. Methods: Total sixty patients of ASA Grade I, II and III, age between 20 and 60 years, who have undergone thoracotomy surgeries were enrolled in the study and randomly divided into two groups of 30 patients each. Group A received 25 mcg/hour of fentanyl patch and Group B received 20 mcg/hour of buprenorphine patch immediately after patient was received in critical care unit postsurgery. Patients were followed for three days. Results: Demographic profile and baseline characteristics were comparable between two groups. Group A had significantly higher level of mean VAS score as compared to Group B at Day 2 and 3. In the same follow up period, both the groups were comparable in regards to mean level of sedation score and hemodynamic variables (HR, SBP and DBP). In Group A 11 (36.66%) patients and in Group B, 8 (26.66%) patients required single dose of rescue analgesic, (p - value > 0.05). The incidence of nausea and vomiting were 13.33% in Group A and 23.33% in Group B. Conclusion: Both the fentanyl and buprenorphine patch are effective and safe in controlling postoperative pain but buprenorphine is better than fentanyl in this respects, as it have longer duration of action and require less rescue analgesic for pain relief.