Cisplatin (CP; cis-diamminedichloroplatinum II) is a drug widely used against different types of solid tumors. Patients receiving CP, however, experience very profound and long lasting gastrointestinal symptoms. Recently, ω-3 polyunsaturated fatty acid-enriched flaxseed/flaxseed oil (FXO) has shown numerous health benefits. The present study was undertaken to investigate whether FXO can prevent CP-induced adverse biochemical changes in the small intestine of rats. A single intraperitoneal dose of CP (6 mg/kg body weight) was administered to male Wistar rats fed with control diet (CP group) and FXO diet (CPFXO group). Administration of CP led to a significant decline in the specific activities of brush border membrane enzymes both in the mucosal homogenates and in the isolated membrane vesicles. Lipid peroxidation and total sulfhydryl groups were altered upon CP treatment, indicating the generation of oxidative stress. The activities of SOD, catalase and glutathione peroxidase also decreased in CP-treated rats. In contrast, dietary supplementation of FXO prior to and following CP treatment significantly attenuated the CP-induced changes in all these parameters. FXO feeding markedly enhanced resistance to CP-elicited adverse gastrointestinal effects. The results suggest that FXO owing to its intrinsic biochemical/antioxidant properties is an effective agent in reducing the adverse effects of CP on intestine.