Due to their high energy storage capacity, phase change materials (PCMs) have received significant attention as thermal energy storage systems. However, their low thermal conductivity reduces the rate of heat transfer. Incorporating nanoparticles into the matrix of PCM can be an efficient way to solve their deficiency. In the current research, nano-enhanced phase change materials (NEPCM) based on Eicosane and incorporated nano graphite were prepared, and their thermal characteristics were evaluated. The SEM micrographs of graphite nano-powders, pure Eicosane, and prepared nanocomposites were analyzed. Differential scanning calorimetry (DSC) and thermal conductivity evaluation (TC) of samples were conducted to determine their heat capacity, thermal diffusivity, and thermal conductivity. The results illustrated that the more graphite nanoparticles, the more collision number between graphite and Eicosane. Therefore, nanocomposites' thermal conductivity and diffusivity are increased with nanophase. Furthermore, increasing crystal growth and reducing heat capacity for the high amount of nanoparticles in the composite were discussed.