In present work, an exergy based thermoeconomic optimization is applied to an actual cascade refrigeration system. The advantage of using exergy method of thermoeconomic optimization is that various elements of the system i.e. condenser, evaporator, compressor and cascade condenser can be optimized separately. A simplified cost minimization methodology based on thermoeconomic concept is applied to calculate the economic costs of all internal flows and products of the system by formulating thermoeconomic cost balance. Once these costs are determined, the system is thermoeconomically evaluated to identify the effects of the design variables on cost of the flows and products. This enables to suggest changes of the design variables that would make the overall system cost effective. Finally, an approximate optimum design configuration is obtained. The result shows that the increase in Coefficient of Performance and exergetic efficiency of the system by 13.76% and 16.20% respectively. The cost of the product and total investment cost are decreased by 19.71% and 19.18% respectively. This shows significant improvement in system performance as well as reduction in the cost of product and total investment cost. The reduction in cost and improvement in performance suggest the commercial acceptability of the cascade refrigeration system in a best efficient way.