Abstract Introduction: There are scarce data comparing different mechanical valves in the aortic position. The objective of this study was to compare the early hemodynamic changes after aortic valve replacement between ATS, Bicarbon, and On-X mechanical valves. Methods: We included 99 patients who underwent aortic valve replacement with mechanical valves between 2017 and 2019. Three types of mechanical valves were used, On-X valve (n=45), ATS AP360 (n=32), and Bicarbon (n=22). The mean prosthetic valve gradient was measured postoperatively and after six months. Results: Preoperative data were comparable between groups, and there were no differences in preoperative echocardiographic data. Pre-discharge echocardiography showed no difference between groups in the ejection fraction (P=0.748), end-systolic (P=0.764) and end-diastolic (P=0.723) diameters, left ventricular mass index (P=0.348), aortic prosthetic mean pressure gradient (P=0.454), and indexed aortic prosthetic orifice area (P=0.576). There was no difference in the postoperative aortic prosthetic mean pressure gradient between groups when stratified by valve size. The changes in the aortic prosthetic mean pressure gradient of the intraoperative period, at pre-discharge, and at six months were comparable between the three prostheses (P=0.08). Multivariable regression analysis revealed that female gender (beta coefficient -0.242, P=0.027), body surface area (beta coefficient 0.334, P<0.001), and aortic prosthetic size (beta coefficient -0.547, P<0.001), but not the prosthesis type, were independent predictors of postoperative aortic prosthetic mean pressure gradient. Conclusion: The three bileaflet mechanical aortic prostheses (On-X, Bicarbon, and ATS) provide satisfactory early hemodynamics, which are comparable between the three valve types and among different valve sizes.