Natural convection in a two-dimensional porous right-angled triangular enclosure having undulation on the left wall is analyzed numerically. The bottom wall is having a sinusoidal temperature and other two walls are maintained at isothermal cold temperature. The stream function-vorticity equations are solved using finite-difference technique. The computations are done on a structured non-orthogonal body fitted mesh. Standard QUICK scheme is used for convective term discretization and diffusive term is discretized using central difference scheme. In this study, the effect of Rayleigh number (Ra = 10(3) - 10(6)), Darcy number (Da = 10(-4) - 10(-2)) and undulations on the left wall is investigated on the heat transfer and fluid flow. It is found that for small Ra, the heat transfer is dominated by conduction across the fluid layers but with the increase of Ra, the process began to be dominated by convection and the undulation on the left wall play an important role in increasing heat transfer. It is also found that heat transfer is also a strong function of Darcy number. As Darcy number increases, heat transfer increases in an appreciable manner. (C) 2013 Elsevier Ltd. All rights reserved.