A detailed study about the free convection over a heated elliptic cylinder, placed at the center of a square cavity having cooled walls, is performed. Simulations are carried out for three Rayleigh numbers (10 4, 10 5, and 10 6) and two cavity aspect ratios (CR=2.5 and 5.0) for different axis ratio (AR). The effect of AR on fluid flow and heat transfer characteristics for varying Rayleigh number and cavity aspect ratio are analyzed. The influence of AR is phenomenal at higher Ra and lower CR. At higher Ra, thermal plumes are observed above the cylinder for different ARs. Bicellular vortices are formed at low Ra by changing CR. The surface-averaged Nusselt number (Nu avg) increases with increasing AR and Ra. The value of Nu avg increases with decreasing CR, and a correlation for Nu avg in terms of AR is obtained for each CR. © 2012 Copyright Taylor and Francis Group, LLC.