Abstract The objective of this work is to examine a transcritical CO2 refrigeration system coupled to a single-effect absorption chiller. The role of the absorption machine is to create a subcooling after the gas-cooler in order to increase the COP. The absorption system is fed by waste heat after the CO2 compressor and so there is not any need for any external energy source. The analysis is conducted with a validated numerical model which is developed in Engineering Equation Solver. The system is studied and optimized for different heat rejection temperatures from 35 °C up to 50 °C and for different refrigeration temperatures from -35 °C up to 5 °C. It is found that there is COP enhancement in all the operating scenarios and especially in the cases with higher heat-rejection temperature and lower refrigeration temperature. The mean COP enhancement is about 23.4% which is an important enhancement for designing more efficient systems.