The present work numerically analyses the heat transfer and entropy generation characteristics in a two-dimensional porous right-angled triangular enclosure with undulations on the left wall. The enclosure is heated sinusoidally from the bottom wall, while the left wall is maintained at a uniform temperature lower than the bottom one and the right inclined wall is adiabatic. The stream function-vorticity formulation with a finite difference scheme has been incorporated to simulate the results. The effects of Rayleigh number, Darcy number and undulations on the left wall on the heat transfer, fluid flow and entropy generation characteristics have been investigated. It has been revealed that for lower values of Rayleigh number, heat transfer is dominated by the conduction mechanism. However, for higher values of Rayleigh number, heat transfer by convection becomes significant. It has been further revealed that for higher values of Rayleigh number and Darcy number, the dominant source of entropy generation is due to fluid friction. Moreover, the entropy generation due to fluid friction is significantly higher in case of undulations on the wall as compared to the cases with no-undulation, whereas the entropy generation due to heat transfer is almost same for both the cases. (C) 2014 Elsevier Ltd. All rights reserved.