© 2022 Aycan Ozdemirkan et al.Introduction. Testicular torsion is a surgical emergency that results in testicular ischemia as a result of rotation of the spermatic cord around itself. Oxidative damage occurs in the testis and distant organs with the overproduction of free radicals and overexpression of proinflammatory cytokines by reperfusion after surgery. In this study, we aimed to investigate the effects of cerium oxide (CeO2), an antioxidant nanoparticle, on lung and kidney tissues in testicular torsion/detorsion (T/D) in rats. Materials and Methods. After ethics committee approval, 24 rats were equally (randomly) divided into 4 groups. Left inguinoscrotal incision was performed in the control (C) group. In group CeO2, 0.5 mg/kg CeO2 was given intraperitoneally 30 minutes before inguinoscrotal incision. In group T/D, unilateral testicular T/D was achieved by performing an inguinoscrotal incision and rotating the left testis 720° clockwise, remaining ischemic for 120 minutes, followed by 120 minutes of reperfusion. In group CeO2-T/D, 0.5 mg/kg CeO2 was given intraperitoneally 30 minutes before testicular T/D. At the end of the experiment, lung and kidney tissues were removed for histopathological and biochemical examinations. Results. Glomerular vacuolization (GV), tubular dilatation (TD), tubular cell degeneration and necrosis (TCDN), leukocyte infiltration (LI), and tubular cell spillage (TCS) in renal tissue were significantly different between groups (p=0.012, p=0.049, p<0.003, p=0.046, and p=0.049, respectively). GV and TCDN were significantly decreased in group CeO2-T/D compared to group T/D (p=0.042 and p=0.029, respectively). Lung tissue neutrophil infiltration, alveolar thickening, and total lung injury score (TLIS) were significantly different between groups (p=0.006, p=0.001, and p=0.002, respectively). Neutrophil infiltration and TLIS were significantly decreased in group CeO2-T/D compared to group T/D (p=0.013 and p=0.033, respectively). Lung and kidney tissue oxidative stress parameters were significantly different between groups (p<0.05). Renal tissue glutathione-s-transferase (GST), catalase (CAT), and paraoxonase (PON) activities were significantly higher, and malondialdehyde (MDA) levels were significantly lower in group CeO2-T/D than in group T/D (p=0.049, p=0.012, p<0.001, and p=0.004, respectively). GST and PON activities were higher, and MDA levels were lower in group CeO2-T/D than in group T/D in the lung tissue (p=0.002, p<0.001, and p=0.008, respectively). Discussion. In our study, cerium oxide was shown to reduce histopathological and oxidative damage in the lung and kidney tissue in a rat testis torsion/detorsion model.