In recent years, the latent heat thermal energy storage using phase change materials (PCMs) has become a hot topic; it has attracted much attention in the utilization of renewable energy sources to improve the energy efficiency of buildings. Isopropyl palmitate (ISOP) with phase transition temperature of 10°C to 13°C and heat of fusion of ~113 J/g was selected to be used as a PCM in building applications. ISOP, 15%, was mixed with plasterboard (PB) as a building material in two techniques, immersion and direct incorporation, in order to retain the ISOP into the porous structure of PB. Scanning electron microscope (SEM) demonstrated that the layer structure of the PB particles was uniformly absorbed by ISOP. Phase transition temperature of ISOP in both techniques determined using differential scanning calorimeter (DSC) is still similar to that of ISOP accompanied with much reduction in the latent heat, particularly in the direct incorporation technique. TCA 300 thermal conductivity analyzer addressed that the thermal conductivity of the PB has been slightly increased with the addition of ISOP. The stored thermal energy performance in a small test room is experimentally investigated. These results indicated that applying ISOP to the south wall of the testing room had the potential to reduce the fluctuation of the indoor air temperature. The effect of ISOP on the mechanical properties of PB has been investigated in the flexural mode using three-point bending test. Moreover, the fire risk of ISOP has been assessed using cone calorimetric. The results confirmed that the novel composite ISOP has a significant opportunity in building applications for thermal energy storage.