The protective effects of black soybean peptides (BSPs) on liver injury induced by high-fat diet in mice were investigated. Healthy male ICR mice were selected and adaptively fed for 7 days, and then randomly divided into a normal group and a model group according to body mass. The mice in the model group were fed high-fat diet continuously for 5 weeks to establish an animal model of liver injury. Afterwards, the mice with liver injury were further randomly divided into 5 groups: model, positive drug, low-dose BSP (400 mg/kg m_b), medium-dose BSP (800 mg/kg m_b), and high-dose BSP (1000 mg/kg m_b). The mice in the experimental groups were orally administered with BSPs for 4 weeks. Physiological and biochemical indicators, inflammatory factors and nuclear transcription factors, and hepatic histomorphological changes in the mice were measured. The results showed that the levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), triglycerides (TG), total cholesterol (TC), malondialdehyde (MDA) and low density lipoprotein (LDL-C) in the mice treated with BSPs significantly decreased (P < 0.05) in comparison with the model group. The contents of glutathione (GSH) and high-density lipoprotein (HDL-C) increased significantly (P < 0.01). The medium and high doses of BSP caused a significant decrease in the levels of interleukin-6 (IL-6), interleukin-1β (IL-1β), tumour necrosis factor-α (TNF-α) and nuclear transcription factor-κB (NF-κB) (P < 0.01). Overall, we concluded that black soybean peptides possess potential antioxidant activity in vivo and reduce lipid peroxidation and inflammatory factors, and thus can be used as a candidate to protect mice from high-fat diet-induced liver injury.