Background Racial and ethnic minority groups are underrepresented among patients undergoing aortic valve replacement in the United States. We evaluated the impact of race and ethnicity on the diagnosis of aortic stenosis (AS). Methods and Results In patients with transthoracic echocardiography (TTE)-confirmed AS, we assessed rates of AS diagnosis as defined by assignment of an International Classification of Diseases, Ninth Revision (ICD-9) and Tenth Revision (ICD-10) code for AS within a large multicenter electronic health record. Multivariable Cox proportional hazard and competing risk regression models were used to evaluate the 1-year rate of AS diagnosis by race and ethnicity. Among 14 800 patients with AS, the 1-year diagnosis rate for AS following TTE was 37.4%. Increasing AS severity was associated with an increased likelihood of receiving an AS diagnosis (moderate: hazard ratio [HR], 3.05 [95% CI, 2.86-3.25]; P<0.0001; severe: HR, 4.82 [95% CI, 4.41-5.28]; P<0.0001). Compared with non-Hispanic White, non-Hispanic Black (HR, 0.65 [95% CI, 0.54-0.77]; P<0.0001) and non-Hispanic Asian individuals (HR, 0.72 [95% CI, 0.57-0.90], P=0.004) were less likely to receive a diagnosis of AS. Additional factors associated with a decreased likelihood of receiving an AS diagnosis included a noncardiology TTE ordering provider (HR, 0.92 [95% CI, 0.86-0.97]; P=0.005) and TTE performed in the inpatient setting (HR, 0.72 [95% CI, 0.66-0.78]; P<0.0001). Conclusions Rates of receiving an ICD diagnostic code for AS following a diagnostic TTE are low and vary significantly by race and ethnicity and disease severity. Further studies are needed to determine if efforts to maximize the clinical recognition of TTE-confirmed AS may help to mitigate disparities in treatment.