The growing environmental concerns and advanced technologies are convincing researchers to revisit CO2 refrigeration. Due to a low critical temperature of CO2, the refrigeration system work in the transcritical cycle for high ambient temperature conditions. It is important to identify the optimum gas-cooler pressure above the critical point to obtain the maximum COP. This paper presents the experimental analysis of the performance of two-stage cooling, low temperature (-31 °C) and medium temperature (-8 to -4 °C) with a booster system and heat recovery. The experimental setup is designed for optimum gas cooler pressure and equipped with a multi-ejector rack to reduce the throttling losses. The effect of gas cooler temperature, receiver pressure and internal heat exchanger (IHEX) on the performance of CO2 refrigeration system are experimentally investigated. It is observed that an optimum receiver pressure exists where the COP is maximum and the system with IHEX has better performance. © 2019 International Institute of Refrigeration. All rights reserved.