Context: The kidney plays a central role in detoxification and excretion of toxic metabolites, and therefore, is susceptible to toxicity by xenobiotics. Objective: To investigate the protective effect of Rosmarinus officinalis (rosemary) powder and its essential (volatile) oil against diethylnitrosamine (DEN)-induced renal injury in rats. Materials and methods: Phenolic and flavonoid components were characterized in rosemary powder using HPLC-UV instrument while rosemary essential oil (E.O) was investigated via GC-MS technique. In rat model, rosemary was administrated orally (in diet) for two months. Lipid profile, antioxidant biomarkers, kidney functions and histopathological examinations were assessed. Results: Hesperidin (4878.88 ppm) and ellagic acid (403.57 ppm) are among the major phenolic and flavonoid constituents in rosemary powder. Camphor (18.36%) and α-pinene (12.74%) represent the main E.O active ingredients. Rats treated with rosemary E.O showed a significant elevation in serum HDL (28.28%) accompanied by a decrease in LDL (115.47%). A significant decrease in serum creatinine and urea was also reported (69.72 and 109.89%, respectively). Moreover, serum glutathione peroxidise (GSH-Px) activity has been significantly increased. Kidney histopathological examinations confirmed the protective effect against DEN-induced abnormalities. Conclusion: Rosemary (powder/E.O) was able to reduce or even prevent the severity of diethylnitrosamine-induced renal dysfunction.