In severe aortic stenosis (AS), there are conflicting data on the prognostic implications of left ventricular (LV) hypertrophy (LVH). We aimed to characterize the LV geometry, myocardial matrix structural changes, and prognostic stratification using cardiac magnetic resonance imaging (CMR) and echocardiography in subjects with severe AS with and without LVH. Consecutive patients who had severe isolated AS and sufficient quality echocardiography and CMR within 6 months of each other were evaluated for LVH, cardiac structure, morphology, and late gadolinium-enhancement imaging. Kaplan–Meier curves, linear models, and proportional hazards models were used for prognostic stratification. There were 93 patients enrolled (mean age 74 ± 11 years, 48% female), of whom 38 (41%) had a normal LV mass index (LVMI), 41 (44%) had LVH defined at CMR by LVMI >2 SD higher than normal, and 14 (15% of the total) with >4 SD higher than the reference LVMI (severely elevated). The Society of Thoracic Surgeons scores were similar among the LVMI groups. Compared with those with normal LVMI, patients with LVH had higher LV end-diastolic and end-systolic volumes, increased late gadolinium-enhancement burden, and lower LV ejection fraction. Most notably, CMR feature-tracking global radial strain, 2-dimensional speckle-tracking echocardiography global longitudinal strain, and left atrial reservoir function were significantly worse. On the survival analyses, LVMI was not associated with a composite of all-cause mortality and/or heart failure hospitalization. In conclusion, compared with normal LVMI, elevated LVMI was not associated with a higher risk of adverse outcomes.