Nanofluids are engineered suspensions of well-dispersed nanoparticles in base fluids such as water, ethylene glycol, propylene glycol, synthetic oil, and other conventional fluids. Since their invention by Choi and Eastman¹  in 1995, nanofluids have attracted tremendous interest from researchers due to their superior thermal properties. Although researchers initially focused on the thermal conductivity, viscosity, and convective heat transfer coefficient of nanofluids,^2–10  recent studies have found that changes in the specific heat and density properties of nanofluids play a very important role in heat transfer applications, such as in heat exchangers and thermal storage devices. Pak and Cho¹¹  were the first to report the specific heat of nanofluids, which has since been investigated by many researchers. Therefore, in this chapter, the experimental characteristics and various prediction correlations of the specific heat of nanofluids are introduced.