Nanofluids have been attracting great attention as new working fluids that can improve the heat transfer performance of cooling devices, leading to energy saving in many mechanical systems owing to their special properties. Therefore, many researchers have investigated the properties of nanofluids, such as thermal conductivity, convective heat transfer coefficient, and viscosity. In addition to these properties, the specific heat and density of nanofluids also play a crucial role in improving their heat transfer performance as these properties are closely related to the heat transfer capacity and thermal storage. Therefore, in this chapter, the experimental characteristics and prediction correlations, including the mechanisms of the specific heat and density of nanofluids, are introduced, based on the results at the present stage. Moreover, state-of-the-art technology for further increasing the specific heat and density of nanofluids is presented.