New types of bio-composite phase change materials (BCPCM) with improved thermal properties were made from spent ground coffee powder (C), beeswax (W) and low density polyethylene (LDPE). Beeswax is a relatively accessible phase change material of organic origin, with a significantly lower unit price compared to conventional phase change materials (PCM). The observations by SEM and FTIR spectroscopy showed that the BCPCMs were physically combined. Through these techniques, it was discovered that ground coffee was effectively impregnated with natural wax and LDPE. According to the thermal gravimetric analysis (TGA), the thermal stability of BCPCM was improved, due to the use of waste coffee grounds, in the working temperature range. The biocomposite possesses excellent performance as characterized by 136.9 J/g (W70C10PE20)>, 127.31 J/g (W70C20PE10)>, 126.95 J/g (W70C30)>, 121.08 J/g (W70PE30) of latent heat storage and tends to decrease the supercooling degree as compared with pure beeswax during melting/solidification process. By adding LDPE to the PCM, the melting time is reduced, demonstrating an improvement in thermal energy storage (TES) reaction time to the demand. The experimental results showed that the fraction of oils (12%) in spent ground coffee powder can participate in the improvement of the thermal properties of BCPMC. The use of biocompatible PCM by-products is suitable for applications in the field of heat storage because it is affordable and environmentally beneficial.