The entropy generation of any thermodynamic system provides a useful measure of the extent of irreversibility. The irreversibility causes the loss of useful work (exergy) in the system and hence the loss of exergy has to be minimized. Entropy generation is one parameter that quantifies the loss of exergy. In this work, the entropy generation of pin fins of circular and elliptical cross sections in cross flow of air is calculated, and their performances are compared with respect to entropy generation. The optimum working parameters for a given geometry and the optimum geometry for the given working parameters are identified for the fins. The entropy generation is calculated for circular and elliptical pin fins with mass constraint.