The problem of laminar natural convection heat transfer in a square cavity with an adiabatic arc shaped baffle is analyzed in this paper. As boundary conditions of the cavity, two vertical opposite walls are kept at constant but different temperatures and the remaining two walls are kept thermally insulated. Results are presented for a range of Rayleigh numbers, arc lengths of the baffle, and shape parameters of the baffle. Finally, parametric results are presented in terms of isothermal lines and streamlines. It is identified that flow and thermal fields are modified by the blockage effect of the baffle. The degree of flow modification due to blockage is enhanced by increasing the shape parameter of the baffle.