Resistin is upregulated in obese humans and mice, and elevated serum resistin induces insulin resistance and hepatic steatosis. Previous studies have revealed that mulberry 1-deoxynojirimycin (DNJ) is important for a variety of physiological processes, especially carbohydrate and lipid metabolism. However, it remains unclear whether DNJ has a positive effect on insulin resistance and hepatic steatosis, and what the exact mechanism is. Male C57BL/6J mice were treated with resistin with or without DNJ. DNJ reversed the homeostasis model assessment of insulin resistance (HOMA-IR)-induced by resistin and significantly decreased triglyceride levels both in the serum and liver. A histological analysis demonstrated that lipid accumulation significantly decreased in the DNJ group compared to the resistin group. A mechanistic analysis showed that DNJ significantly inhibited the resistin-induced decline in enzyme activities of hormone-sensitive lipase (HSL) and hepatic lipase (HL) in serum and lipoprotein lipase (LPL) in liver. FAS and Acox13α were significantly altered by resistin but restored by DNJ. Furthermore, DNJ partially but significantly restored insulin-stimulated glucose uptake compared with the resistin group, suggesting that DNJ reversed the insulin sensitivity impaired by hyperresistinemia. Treatment of AML12 cells with DNJ significantly restored the expression level and phosphorylation of Akt. The transcriptional levels of InsR and IRS1, as well as the protein levels of InsR and Glut4 and phosphorylation of PI3K and GSK3β, were also normalized in the DNJ-treated group. In conclusion: mulberry DNJ significantly alleviated liver steatosis and insulin resistance in hyperresistinemia.