Objective: Prosthesis-patient mismatch (PPM) of the aortic prosthesis is frequent trouble following aortic valve replacement (AVR). The residual high transprosthetic pressure gradient (PG) could interrupt left ventricular mass regression (LVMR). The purpose of this study was to assess the frequency of PPM as well as its impact on LVMR postoperatively. Methods: 106 patients were prospectively evaluated after AVR for aortic stenosis (AS) from Jan 2016 to Dec 2021. Patients were classified into three groups based on the effective orifice area index (EOAI) (cm2 /m2 ); Group A (≥0.85), B (0.8-0.84), and C (< 0.8). Follow-up of LVMR was performed postoperatively on all patients after six months. Results: We didn’t record significant changes in basic data among studied groups away from the basal surface area, which was substantially higher in group C (Mean 2.4, P<0.001). The PPM incidence was observed in 30 survivors (28.3%); 12 survivors in group B and 18 survivors in group C. All groups showed a substantial reduction in posterior wall thickness (P<0.001). However, a significant decrease in peak and mean PG, LVM index, and diameter of the interventricular septum was only observed in groups A and B. Conclusions: PPM with EOAI below 0.85 cm2 /m2 leads to high residual transprosthetic PG and subsequent impairment in LVMR. Therefore, meticulous choosing of the valve size with the availability of alternative options could prevent PPM squeal. Keywords: Aortic valve replacement, Patient prosthesis mismatch, Prosthesis, LV, PPM