Background: Previous studies have demonstrated that platelet activation occurs in patients with aortic stenosis (AS). This study sought to evaluate the changes in hematologic and clinical parameters noted with the improvement in AS following transcatheter aortic valve implantation (TAVI) in patients with severe AS at high risk of surgery. Patients and Methods: The study included 33 patients who underwent TAVI. In addition to biochemical, clinical, and echocardiographic examinations, hematologic blood parameters were recorded before TAVI, at discharge, and at 1 and 4 months. Results: Mean platelet volume (MPV) showed a progressive decrease after TAVI. On echocardiography at 1 month, aortic valve area significantly increased, with significant decreases in peak and mean gradients. Progressive decreases were also noted in N-terminal proB-type natriuretic peptide levels. Conclusion: Our findings show that TAVI improves hemodynamic parameters of the valve with marked clinical and echocardiographic improvement, resulting in decreased platelet activation and MPV in patients with severe AS.