The use of evaporative cooling techniques for pre-cooling the inlet air of a condenser used in air conditioning applications has proven to be very effective in improving its performance. Ultrasonic techniques constitute a promising alternative to improve the design of evaporative pre-cooling systems. Compared to direct spray cooling applications, not only they eliminate the pressure loss induced in the inlet air stream but also, they are capable of generating smaller droplet sizes with reduced power consumption than a high-pressure spray nozzle. This paper deals with an experimental investigation of an ultrasonic spray atomiser used to pre-cool the air entering to the condenser of a heat pump used in air-conditioning applications. A set of 12 experimental tests were conducted on a test bench consisting of a subsonic wind tunnel with an ultrasonic spray atomiser installed in the test section. The influence of the air velocity and mass flow rate of sprayed water (depending on the number of active atomisers) on the performance of the system was investigated. The results of the study show the pre-cooling capacity of this system, under different operating conditions, through several performance indicators: evaporative cooling efficiency (saturation efficiency), temperature drop, wet bulb depression and evaporated water efficiency. The highest values of evaporative cooling efficiency occur in the low speed range of the tested airflows, for configurations of the atomisation system with a high number of active atomisers, and it has been found that the evaporative pre-cooling process is not homogeneous throughout the airflow for some operating conditions.