Thoracic aortic disease, including thoracic aortic aneurysm (TAA), is frequently seen in patients with bicuspid aortic valve (BAV). We hypothesized that BAV morphotype would be associated with aortic aneurysm phenotypes but that other patient variables would significantly modify this relationship. 829 patients between 18 and 90 years with BAV and available raw imaging of the aortic valve and the ascending aorta to its mid-portion prior to aortic valve and aortic surgery were examined. The sinuses of Valsalva and proximal ascending aorta were measured from 2-dimensional co-planar echocardiographic images. We observed strong associations between patient habitus and raw and normalized dimensions of the aortic root and ascending aorta. Patients with R–L morphotype presented at an older age with larger aortic root but similar ascending aortic dimensions. After accounting for patient morphometric characteristics and severity of aortic valve disease, patients with R–L valve morphotype were marginally more likely to have an aortic root aneurysm (86% vs. 78%; P = 0.043), defined as aortic root dimension Z score ≥3. We observed only small differences in aortic dimensions between BAV morphotypes, that are eclipsed by variation in patient habitus. We interpret these findings to mean that BAV patients will not likely benefit from therapies based on aortic valve morphotype. Rather, we propose that all BAV patients should undergo longitudinal follow-up, independent of valve morphotype. Guidelines for aortic surgery based upon dimensions alone may be improved by considering patient characteristics such as age, body size and other characteristics.