Nanoparticles-containing working fluid utilization in thermal systems has been increasing day after day because of their capabilities of enhancing thermophysical properties of the base fluid. In this experimental study, influences of nanoparticle utilization inside the polyol ester compressor oil in a cooling system as a nanolubricant were investigated. Titanium dioxide nanoparticles were added to the polyol ester compressor oil, together with 350 g of an R134a refrigerant. A surface active agent was also used in order to prevent agglomerations of doped nanoparticles during operation of the system. Experiments were conducted at different nanoparticle concentrations (1.0 wt.%, 1.5 wt.%, and 2.0 wt.%) to show the effects of nanoparticle concentration on performance of the cooling system. Cooling coefficient of performance and power consumption of the compressor were analyzed. As a consequence of the experiments, the best results were obtained in the cases in which nanoparticle concentration of 1.0% nanolubricant was used. The cooling coefficient of performance of the system was increased up to 4.70, and the power consumption of the compressor was decreased to 26.28 kJ.h(-1).