A computational fluid dynamic simulation of a mechanical heart valve closing dynamics in the mitral position was performed in order to delineate the fluid induced stresses in the closing phase. The pressure and shear stress fields in the clearance region and near the inflow (atrial) side of the valve were computed during the mitral heart valve closure. Three separate numerical simulations were performed. The atrial chamber pressure was assumed to be zero in all the simulations. The first simulation was steady flow through a closed mitral valve with a ventricular pressure of 100 mm Hg (1.3 kPa). In the second simulation, the leaflet remained in the closed position while the ventricular pressure increased from 0 to 100 mm Hg at a rate of 2000 mm Hg/s (simulating leaflet closure by gravity before the ventricular pressure rise - gravity closure). In the third case, the leaflet motion from the fully open position to the fully closed position was simulated for the same ventricular pressure rise (simulating the normal closure of the mechanical valve). Normal closure (including leaflet motion towards closure, and sudden stop in the closed position) resulted in a relatively large negative pressure transient which was not present in the gravity closure simulation. The wall shear stresses near the housing and the leaflet edge close to the inflow side were around 4000 Pa with normal closure compared to about 725 Pa with gravity closure. The large negative pressure transients and significant increase in wall shear stresses due to the simulation of normal closure of the mechanical valve is consistent with the previously reported increased blood damage during the closing phase.