The second law of thermodynamics analysis is a powerful tool for evaluating and improving the efficiency of energy systems. In this study, viscous entropy generation in the airflow around airfoils used in wind turbine blades was investigated using computational fluid dynamics (CFD). The flow around these sections was simulated at a given Reynolds number and angles of attack ranging from 0° to 20°. For each airfoil, the local distribution of the entropy generation rate was presented, and the effects of phenomena such as flow separation on entropy generation were carefully examined. The results show that flow separation and the increase in shear layer thickness in the wake region of the airfoils significantly enhance entropy generation. For example, with the increase in angle of attack and the growth of the separation bubble at 20°, a much thicker shear layer forms at the trailing edge of the airfoil, leading to a considerable increase in viscous entropy generation. In addition, a close correlation was observed between generated entropy and the drag coefficient, such that the variation of entropy generation with angle of attack exhibits an exponential behavior similar to that of drag. Based on this, the second law efficiency of the flow around each airfoil was calculated, and its variation with angle of attack was reported.