© 2017 American Society of Echocardiography Background The human aorta dilates with advancing age. However, the association between progressive aortic dilation with aging and cardiac remodeling has not been established in studies of community-dwelling adults. The aim of this study was to test the hypothesis that there would be a relationship between aortic size increase over the early adult life span with left ventricular (LV) structural remodeling and subclinical LV dysfunction in middle age, even in the absence of overt cardiovascular and valvular disease. Methods Included were Coronary Artery Risk Development in Young Adults study participants (N = 2,933) aged 23 to 35 years with available transthoracic echocardiographic measurements during 20 years of follow-up. Multivariate linear regression models assessed sex-specific associations between 20-year change in aortic root diameter with LV structure and function. Results Larger aortic root diameter at 20-year follow-up was associated with greater LV mass (2.77 vs 2.18 g/mm in men and women, respectively, P <.001). In longitudinal analyses, increase in aortic root diameter over 20-year follow-up was associated with a greater 20-year increase in LV mass and ratio of LV mass to LV end-diastolic volume ratio in both sexes. In women but not in men, increased aortic root diameter over 20 years was associated with increased left atrial dimension, impaired E/E′ and impaired early diastolic longitudinal and circumferential strain rates assessed by speckle-tracking echocardiography. Conclusions Progressive increase in aortic root diameter from early adulthood to middle age was associated with increased LV mass and LV concentric remodeling in both sexes and impaired diastolic function predominantly in women.