The design and optimization of electronics cooling systems is not easily accomplished through conventional analysis tools such as analytical and numerical methods. The enhancement in thermal performance causes a rise in pressure drop, which increases the load of pumping power. Consequently, the overall assessment of cooling system requires a trade-off between thermal performance and pressure drop. Entropy generation minimization (EGM) method is based on the theory that a thermodynamically optimized system is the least irreversible, or minimum entropy generation in the system. EGM method has been used as an optimization tool in thermodynamic systems for a broad range of engineering fields, but its reliability and accuracy has not been investigated. In this study, the fin pitch of a plate fin heat sink in free convection environment was optimized by EGM method. Results were compared with both analytical and numerical optimization results. The EGM method predicted slightly higher fin pitch than the analytical and CFD methods but with the same trend. The discrepancy between the analytical and EGM method was within 7-12%, while that between the CFD and EGM method was 5-9%. With this small discrepancy, it was concluded that the EGM method was very reliable to be used in the fin pitch optimization of the plate fin heat sink subject to free convection.