Heat exchangers play an essential role in the energy conversion processes of both fossil fuel and renewable sources. Due to its capacity to accommodate various dimensions, occupied space, low-pressure penalty, and low initial investment, MPFHE (Multistream Plate Fin Heat Exchanger) has been utilized in many energy conversion processes, particularly in cryogenic cycles. Any improvement in an MPFHE leads to increases in efficiency and sustainability and, consequently, to mitigation of energy consumption and maintenance cost of a cycle where it is applied. In this research work, the optimization of an MPFHE with four operating streams is conducted, having the extended surface's geometric design parameters and types as input variables and thermo-hydraulic performance as the objective function. The MPFHE rating and sizing are based on heat transfer calculations using the HTFS correlations. Due to a large number of input variables, the Non-Sorting Genetic Algorithm (NSGA-II) has been used chosen for the optimization. During the optimization, parameters such as Reynolds number, heat transfer coefficient, pressure drop, and heat load are monitored and reported. The optimization results significantly improve the heat exchangers' thermal-hydraulic performance. The optimal configuration of the heat exchangers shows a considerable heat transfer enhancement in the heat exchangers by up to 1.5 % and a significant reduction in power consumption by up to 11.1 % compared to the existing configuration, leading to a significant improvement in the overall performance of the cryogenic unit.