Objective: Testicular torsion is a condition that often occurs as a result of the rotation of the spermatic cord in childhood and adolescence in men, manifests with acute pain and causes infertility in the future even if emergency intervention is performed. The aim of this study is to investigate the protective and preventive effects of fentanyl, a potent analgesic agent frequently used in anaesthesia practice, on testicular ischemia–- reperfusion injury, which manifests through acute pain. Methods: A total of 16 adult male Wistar rats, weighing 200-250 g, were used in this study. They were divided into two groups, consisting of eight animals in each group. Torsion was created in all rats by rotating left testicles 720 clockwise on the day of the experiment. 3 mM of fentanyl was applied intraperitoneally 30 minutes before detorsion to the fentanyl group. Following an hour of ischemia, the left testicle was reinstated, and tissues were repaired according to their physiology. Following 24 hours of reperfusion, the animals were euthanised after taking left testes and blood samples. Results: Fentanyl, administered prior to testicular detorsion, significantly suppressed germ cell damage in torsioned tissue, catalase activity and malondialdehyde levels in blood samples taken from the heart. No significant differences were observed in plasma total thiol concentration, histological score, Leydig cell counts, percentage of necrosis and tubule rupture. Conclusion: These findings show that fentanyl administered before detortion creates a protective effect by preventing testicular ischemia–- reperfusion injury leading to infertility in the future.