Large chromosomal clonal mosaic events (CMEs) have been suggested to be linked to aging and to predict cancer. Type 2 diabetes (T2D) has been conceptualized as an accelerated-aging disease and is associated with higher prevalence of cancers. Here we aimed to assess the association between T2D and CME occurrence in blood. We evaluated the presence of CMEs in 7,659 individuals (including 2,208 with T2D) using DNA arrays. A significant association between CME occurrence and T2D was found (odds ratio (OR) = 5.3; P = 5.1 × 10(-5)) and was stronger when we only considered non-obese individuals with T2D (OR = 5.6; P = 4.9 × 10(-5)). Notably, CME carriers with T2D had higher prevalence of vascular complications than non-carriers with T2D (71.4% versus 37.1%, respectively; P = 7.7 × 10(-4)). In CME carriers, we found an increase in the percentage of abnormal cells over 6 years (P = 8.60 × 10(-3)). In conclusion, given the increased risk of cancer in CME carriers, our results may have profound clinical implications in patients with severe T2D.