Numerical investigation of mixed convective in a vented square cavity with fin. The horizontal walls are adiabatic, while the left and right walls are at hot and cold temperatures, respectively. The fluid inlet to the cavity from the lower left open area, and exit from the upper right open area. In this study, a finite element scheme is employed. The analysis is done for specific Prandtl number, Reynolds number, fin length, Richardson number, and the location of the fin. The finding indicates that the increases when high the location of the fin is, the increase at the maximum height of this fin location is estimated to be 17% due to an increase in the area of fluid flow on the hot wall caused by rising convective. The highest heat transfer occurs when the fin length is equal to 0.6 at the location.