A high intake of green leafy vegetables rich in antioxidative nutrients such as vitamin C and β-carotene may protect against the risk of type 2 diabetes. Measurement of the circulating nutrient concentrations can indicate the nutrient status more directly, and vitamin C and carotenoids are recognized as good biomarkers for the intake of fruits and vegetables. The aim of this study was to investigate the relationships between serum antioxidative vitamin concentrations and type 2 diabetes in Japanese subjects. The study subjects comprised 506 men and 493 women who first underwent anti-aging health checks at Tokai University Tokyo Hospital. Serum concentration of vitamin (V) A, VC, α-tocoferol, β-carotene, VB12, folate, ferritin and homocysteine, and fasting plasma glucose and HbA1c were used for analysis. Low levels of β-carotene and VC were significantly associated with dysglycemia. Diabetic subjects showed significantly decreased β-carotene and VC levels, and multivariate analyses suggested that low levels of β-carotene and VC were factors related to diabetes. Low levels of β-carotene and VC are significantly related to dysglycemia/type 2 diabetes, and encouraging people at a higher risk of diabetes to take more green vegetables may be useful as a dietary intervention to improve the antioxidative vitamin status and dysglycemia.