Background/aim: Transcatheter aortic valve implantation (TAVI) is an innovative approach to the treatment of aortic stenosis (AS) as an alternative to surgery in high-risk patients. Mean platelet volume (MPV) is considered an indicator of endothelial dysfunction, platelet function, and activation. In this study, we aimed to investigate MPV changes in patients undergoing TAVI. Materials and methods: This study included 100 patients diagnosed with symptomatic severe AS and treated with TAVI between July 2011 and August 2013. Hematological parameters of the patients were examined prior to the procedure and 24 h, 1 month, and 6 months after TAVI. Results: A statistically significant change in patients' MPV was detected after TAVI compared to the baseline situation (P: 0.001). While no statistically significant change was observed on the first day after TAVI, at discharge, compared to the baseline situation, a statistically significant decrease was seen 1 month and 6 months after discharge. Conclusion: We have demonstrated a decrease in MPV after surgery compared to the value before surgery. We have sought to propound the change in MPV as an indication of endothelial function after TAVI.