Biologically produced Nano-selenium (Nano-se) considers one of the less toxic element in comparison with the other forms of selenium. The present study evaluated the protective effect of biologically Nano-se against early hepatocarcinogenesis induced by diethyl nitrosamine (DEN) for 1 week in rats. Forty male Wister rats were divided into four groups as follows: Group 1 treated with intraperitoneal (i.p.) injection with physiological saline once and kept as control; group 2 treated with DEN alone (200 mg/kg) i.p. injection once; group 3 treated with both DEN and Nano-Se and group 4 treated with Nano-Se alone (0.5 mg/kg) orally by gastric intubation. DEN administration did not alter the erythrogram but induced significant changes in leukogram represented by increase in total leukocytic count (TLC), neutrophil and monocyte cell counts together with significant reduction in lymphocyte and eosinophil cells count (P ≤ 0.05). DEN induced hepatotoxicity noticed through an elevation of serum hepatic enzymes such as AST, ALT and γ-GT. Additionally, an increase in the oxidative stress marker as malondialdehyde content (MDA) and reduction of antioxidant parameters such as catalase (CAT) and reduced glutathione (GSH) were observed. Moreover, DEN was associated with the formation of putative hepatic foci indicated with over expression of glutathione transeferase –placental form (GST-P) immunostaining. Interestingly, Nano-Se clearly alleviated the negative impacts of DEN induced hepatotoxicity via returning leukogram to normal condition, suppressed the elevated of serum hepatic enzymes, oxidative stress markers, decrease positive GST-P foci and remarkably increased the antioxidant capacity. Therefore, biological produced Nano-se might be considered as an effective strategy in hepatic cancer chemoprevention.