A new kind of phase change material n-octadecane microcapsules containing peppermint fragrance scent has been synthesized through the interfacial polymerization of isophorone diisocyanate (IPDI) and hexamethylenediamine (HMDA). The average size, morphology, and chemical components of the microcapsules were characterized by laser particle size analyzer, scanning electron microscope (SEM), and Fourier transform infrared (FTIR), respectively. The thermal characterizations of the microcapsules were studied by differential scanning calorimetry (DSC) and thermal gravity analysis (TGA). The results show that the average size of the microcapsules was in the range of 4.0 to 7.0 mu m and decreased with increasing emulsifier. The microcapsulated phase change materials (MicroPCMs) are spherical, and their surface is dented. The MicroPCMs without nucleating agents demonstrated high heat storage capacity but had supercooling phenomena. It was found that the addition of approximately 8.3 wt % nucleating agents 1-tetradecanol or paraffin in core materials can suppress MicroPCMs from supercooling. The MicroPCMs maintained a good thermal stability below 150 degrees C.