Composite materials are a combination of several materials to form a new material with specific properties. Chemical compatibility of the constituent materials is a factor that affects the characteristics of composite materials. Currently, composite phase change materials (PCM) are commonly applied as thermal energy storage systems. This study investigated the characteristics of beef tallow/rice husk charcoal/plaster PCM composite. The weight fraction of rice husk charcoal used was 10%. To prevent leakage of beef tallow from the composite structure, the researcher used polyvinyl acetate (PVAc) to cover the tallow/RHC composite before mixing it with plaster material. As much as 30% of the tallow/RHC/PVAc composite weight fraction is integrated into the plaster. PCM composite was made by using a direct incorporation method. The FTIR test results on the PCM composites produced showed good chemical compatibility among different components. The scanning electron microscope results showed the formation of microcapsules where the rice husk charcoal and polyvinyl acetate functions as a wrapper/capsule for beef tallow. This composite is suitable for application in building walls as thermal energy storage.