AIMS: To examine whether the excess risks of coronary heart disease (CHD), stroke, dialysis, and lower extremity amputation (LEA) associated with type 2 diabetes mellitus (T2DM) differ across age, sex, and ethnicity in Singapore. METHODS: Using a 10-year administrative data, we matched individuals with T2DM using nearest neighbour matching, to those without, in 1:2 ratio. To examine whether the excess risks were heterogeneous across age, sex, and ethnicity, we generated interaction terms of age, sex, and ethnicity with T2DM status in Cox proportional hazard (PH) models. RESULTS: The main analyses included ~1 million person years, comprising 66,099 and 120,485 individuals with and without T2DM, respectively. The associations of T2DM with CHD and dialysis, split into two time periods to address violation of PH assumption, were higher with older age in short-term but lower with older age in long-term. The association of T2DM with stroke and LEA were lower with older age. The associations of T2DM with CHD and stroke were also consistently higher in women than men. The associations of T2DM with LEA were higher in ethnic Malays than ethnic Chinese. CONCLUSIONS: The excess risks of CHD, stroke, dialysis, and LEA associated with T2DM were heterogeneous across some demographic subgroups.