An experimental investigation was completed on nanoparticle-enhanced ionic liquid (NEIL) heat-transfer fluids (HTFs) as an alternative to conventional organic-based HTFs. These nanoparticle-based HTFs have the potential to deliver higher thermal conductivity than the base fluid without a significant increase in viscosity at elevated temperatures. The effect of nanoparticle morphology and chemistry on thermophysical properties was examined. Whisker-shaped nanomaterials were found to have the largest thermal conductivity temperature dependence and were also less likely to agglomerate in the base fluid than spherical-shaped nanomaterials.