Although most patients with severe aortic stenosis (AS) have high aortic valve velocities, outcomes of transcatheter aortic valve replacement (TAVR) in patients with extremely high aortic valve velocities remain unclear. We aimed to investigate the clinical outcomes of patients with peak aortic jet velocity (Vmax) values ≥ 6 m/s. The study included 913 consecutive patients who underwent TAVR between 2013 and 2020. To better understand the impacts of the higher Vmax on outcomes, patients with Vmax values < 4.0 m/s, ejection fractions < 50%, valve-in-valve procedures, and unstable hemodynamics were excluded. Patients were grouped according to preprocedural Vmax as follows: 4-5 m/s, 5-6 m/s, and ≥ 6 m/s. According to guidelines describing Vmax ≥ 5.0 m/s as "very" severe AS, Vmax ≥ 6.0 m/s was defined as "extremely" severe AS in this study. New York Heart Association classification-III/IV and severe left ventricular hypertrophy were more frequent in the extremely severe AS group, which concurred with the advanced stage of severe AS, and they had a similar mortality rate to the other groups. Although they showed the greatest Vmax improvements after TAVR, they had higher paravalvular leak (PVL) rates. Even among the patients who received newer-generation transcatheter aortic valves, they had higher PVL rates, despite more frequent balloon dilation than the other groups. Although patients with extremely severe AS have similar mortality rates to other patients with severe AS after TAVR, the risk of procedural complications caused by more frequent balloon dilation should be considered.