Aim: Melatonin-selenium nanoparticle (MT-Se), a novel complex, was synthesized by preparing selenium nanoparticles in a melatonin medium. The present investigation was designed to determine the protective effects of MT-Se against lipopolysaccharide (LPS). Methods: The model of immunological liver injury in mice was prepared. The levels of alanine aminotransferase, aspartate aminotransferase, nitric oxide (NO) in serum, malondialdehyde content, superoxide dismutase (SOD), and glutathione peroxidase (GSH-px) activities in a liver homogenate were assayed by spectrophotometry. The content of tumor necrosis factor-α (TNF-α) and interleukin- 1 (IL-1) were determined by ELISA. The splenocyte proliferation was assayed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetra-zolium bromide (MTT) dye reduction. Meanwhile, a hepatic pathological examination was observed. Results: In the BCG/LPS-induced hepatic injury model, MT-Se administered at doses of 5, 10, or 20 mg/kg to the BCG/LPS-treated mice for 10 d significantly reduced the increase in serum aminotransferase, reduced the severe extent of hepatic cell damage and the immigration of inflammatory cells. It also attenuated the increase in the content of thiobarbituric acid-reactive substances and enhanced the decrease in activities of SOD and GSH-px. In contrast, the treatment with MT-Se suppressed the increase in NO level in both the serum and liver tissue. Furthermore, MT-Se significantly lowered an increase in TNF-α and IL- 1 β levels in the liver and inhibited the production of TNF-α and IL- 1 β by peritoneal macrophages. A downregulation effect of MT-Se on splenocyte proliferation was also observed. Conclusion: MT-Se showed a hepatic protective action on immunological liver injury in mice.