In the past decade, nanofluids have proven effective for heat transfer enhancement of many thermal engineering applications. This is due to their superior thermal performance characteristics compared with conventional coolants. Therefore, the adoption of nanofluids as alternative coolants in proton exchange membrane fuel cell (PEMFC) cooling systems is considered a novel technology and a promising contributor to the solution of thermal management problems that are impeding the commercialization of automotive PEMFC engines. In this article, the thermal performance enhancement of a radiator was experimentally investigated through the addition of Zinc oxide (ZnO) and aluminum nitride (AlN) nanoparticles suspended in a 50/50 mixture of water and ethylene glycol (WEG) as the base fluid for automotive PEMFC cooling systems. The nanofluid concentrations of 0.2 wt% and 0.5 wt% from nanoparticles were used, and the inlet temperature range of the nanofluids was 50 degrees C to 80 degrees C. The experimental results indicate that the heat transfer rate and radiator effectiveness were improved with high flow rates of the base fluid and nanofluid. Furthermore, by increasing the mass concentration of nanoparticles, the heat transfer rate, overall heat transfer coefficient, and radiator effectiveness were enhanced. This can be explained by the significant enhancement of thermal conductivity and Brownian motion benefited from nanofluids. Compared with the base fluid, the heat transfer rate increased by 24.3% and 57.7% at concentrations of 0.2 wt% and 0.5 wt% ZnO nanoparticles, respectively, within the considered temperature range. Meanwhile, the AlN/WEG nanofluids enhancements achieved 15.3% and 30.7% at the same concentrations. In conclusion, the use of ZnO nanoparticles is strongly recommended for suspension in the WEG (50/50 v/v) mixture as a proper coolant for better performance of PEMFC-based engines.