Maintaining a suitable temperature for the photovoltaic (PV) module is of great significance but a challenge. Herein, a low-supercooling phase change material (PCM) nanoemulsion was developed as a promising coolant for use in the PV module thermal management system. OP35E was used as the paraffinic PCM and the phase change characteristics and thermophysical properties of the as-prepared PCM nanoemulsions were investigated. It is shown that OP35E-nanoemulsions possess a melting point of roughly 34 °C and ignorable supercooling. The apparent specific heats of low-supercooling OP35E-nanoemulsions are 2.29–3.29 times that of water at the phase transition range, and its viscosities is slightly higher than that of water. Furthermore, the thermal management performance of water and OP35E-nanoemulsions on PV modules was evaluated. Compared with water, the PV module temperature further reduced by 5.3% when employing 20 wt% OP35E-nanoemulsion. More importantly, using 10 wt% and 20 wt% OP35E-nanoemulsions only required less than 50% of the pumping power consumption of the water-cooling system to reduce the PV module temperature to the same. On the contrary, owing to the lower apparent specific heat caused by the futile latent heat, the OP35E-nanoemulsion with large supercooling exhibited the worst thermal management performance with the highest PV module temperature and pumping power consumption, and lowest output power. Therefore, the outstanding characteristics and better cooling performance than water of the low-supercooling nanoemulsions make them show great potential in the PV module thermal management system as a novel kind of heat transfer fluids with improved specific heat.