An experimental evaluation of a cascade refrigeration system prototype using NH3 and CO2 as refrigerants has been performed. The prototype is used to supply a 9-kW refrigeration capacity to a horizontal plate freezer at an evaporation temperature of -50 degrees C as design conditions. The prototype includes a specific control system and a data acquisition system. The article describes the prototype and the experimental program carried out to study the freezing process in the horizontal plate freezer. The experimental results include the freezing time, the temperature evolution in the product to be frozen, the refrigeration capacity of the facility, the electric power of the compressors, the coefficient of performance (COP) of the low-and high-temperature systems, and the overall system COP. The results obtained would confirm that the use of CO2 in plate freezers represents a viable alternative to refrigerants currently in use.