Mealworms (Tenebrio molitors larvae) have a high quality and quantity of amino acids and protein that have attracted attention as an alternative nutrition resource. This study examined the anti-hyperglycemic effects of fermented mealworm extract (MWF) in db/db mice. The mice were fed with or without MWF for six weeks. MWF was administered orally to the mice at 200 mg/kg body weight/d. MWF improved the fasting blood glucose level and glucose intolerance significantly compared to the control group. Insulin immunohistochemistry staining showed that the insulin levels of pancreatic β-cells in the MWF group were higher than those of the control group. MWF increased the hepatic glycogen content and the related gene levels, such as glucose transporter 2 and glycogen synthase 2. Thus, MWF lowered the blood glucose levels by up-regulating glucose uptake and glycogen synthesis-related gene expression. These results suggest that MWF can be used as a new natural anti-diabetic resource for type 2 diabetes.