Background Substantial aortic calcification is known to be associated with aortic stiffening and subsequent left ventricular (LV) hypertrophy. This study examined whether the thoracic aorta calcium score (TACS) is related to LV hypertrophy and whether it leads to an adverse prognosis in patients with severe aortic stenosis (AS) after aortic valve replacement (AVR). Methods We retrospectively reviewed 47 patients (mean age, 64 ± 11 years) with isolated severe AS who underwent noncontrast computed tomography of the entire thoracic aorta and who received AVR. TACS was quantified using the volume method with values becoming log transformed (log TACS+1). Transthoracic echocardiography was performed before and 1 year after the operation. Results Preoperative LV mass index (LVMI) displayed significant positive correlations with male gender ( r  = 0.430, p  = 0.010) andlog (TACS+1) ( r  = 0.556, p  = 0.003). In multivariate linear regression analysis, onlylog (TACS+1) was independently associated with LVMI, even after adjusting for age, gender, transaortic mean pressure gradient, and coronary or valve calcium score. Independent determinants for postoperative LVMI includedlog (TACS+1) and preoperative LVMI after 1 year of follow-up echocardiography, adjusting for age, gender, indexed effective orifice area, and coronary or valve calcium score. During a median follow-up period of 54 months after AVR, there were 10 events (21%), which included 4 deaths from all-causes, 3 strokes, 2 inpatient admissions for heart failure, and 1 myocardial infarction. The event-free survival rate was significantly lower for patients with TACS of 2,257 mm3 or higher compared with those whose TACS was lower than 2,257 mm3 (log-rank p < 0.001). Conclusions High TACS was associated with increased LVMI among patients with severe AS. Further, high TACS usefully predicted less regression of LVMI and poor clinical outcomes after AVR. TACS may serve as a useful proxy for predicting LV remodeling and adverse prognosis in patients with severe AS undergoing AVR.