The antidiabetic action of mangiferin (MF) with exercise was investigated in KK-Ay mice, an animal model of type 2 diabetes. MF (30 mg/kg) significantly decreased the blood glucose and insulin level of KK-Ay mice with exercise 2 weeks after the oral administration, while control group (exercise only) did not change. MF also significantly decreased blood triglyceride level of KK-Ay mice. These findings indicate that MF with exercise is useful for the early stage symptom of type 2 diabetes.