Display omitted ► We investigated a space CO2 condenser’s heat transfer coefficient and pressure drop. ► A CO2 condenser with mini-channel of 0.9mm. ► HTCs agree with the prediction by Thome correlation within errors of ±30%. ► Flow pressure drops agree with the prediction by Friedel correlation within errors of ±30%.. We present the flow condensation heat transfer characteristics of CO2 in a mini-channel condenser. The condenser consists of seven tubes in parallel, which are thermally connected to two aluminium base-plates by using thermal glue. At saturation temperatures ranging from −5°C to 15°C, with mass velocities of 180, 360 and 540kg/(m2s), respectively, and average vapour qualities from 0.2 to 0.8, we obtained the CO2 condensation heat transfer coefficients, ranging from 1700 to 4500W/(m2K). We compared the measured heat transfer coefficients with those predicted by the established correlations, and found that Thome’s was applicable to the condenser under investigation, with deviation less than 30%. We also discussed the measured pressure drop over the condenser, which increased with the mass velocity and the vapour quality, but decreased with the saturation temperature.