The aim was to analyse the relationship between metabolic syndrome and type 2 diabetes mellitus risk among the aged. This was a prospective population-based study, with a 9-year follow-up. All subjects of the municipality of Lieto in Finland aged ≥64 in 1998-1999 with no type 2 diabetes mellitus at baseline (n=1117) were included. Hazard ratios for incident type 2 diabetes mellitus predicted by metabolic syndrome (defined by modified International Diabetes Federation criteria) were estimated. During the 9-year follow-up, a total of 69 participants (6.2%) developed type 2 diabetes mellitus. After multivariable adjustment (age, gender, smoking, frequency of exercise, cardiovascular disease and low-density lipoprotein-cholesterol), type 2 diabetes mellitus (hazard ratio, 95% confidence interval) (3.15, 1.89-5.25, p < 0.001) was more common in subjects with metabolic syndrome compared to subjects without it. Evaluating metabolic syndrome components individually, impaired fasting glucose (5.09, 2.64-9.82, p < 0.001) and obesity (1.71, 1.05-2.97, p = 0.034) predicted a higher incidence of type 2 diabetes mellitus. Our findings suggest that metabolic syndrome predicts onset of type 2 diabetes mellitus even in late life. Impaired fasting glucose and obesity should be targets for primary prevention of diabetes among the aged with metabolic syndrome.