This study is aimed at developing a thermoplastic composite based on date pit powder waste for use as a thermal insulator in building industries. Date pits are the by-product of date stoning, either for the production of pitted dates or for the manufacture of date paste. The date pit powder (DPP) used in this study was obtained from the UAE University farm in Al Foah, UAE. DPP waste contents ranging from 0 wt.% to 50 wt.% were used to prepare the DPP-polystyrene composite. Date pit powder was mixed with polystyrene using a melt extruder, and then the mixture was transferred to the hot press to produce the final sample. The thermal and physical characteristics of the produced composites were measured experimentally and analyzed theoretically in terms of date pit and polystyrene properties. The characterized properties of the DPP-polystyrene composites, namely, density, thermal conductivity, water retention, thermal stability, and microstructure, showed that a stable composite material with insulation and construction capacity can be formed by the addition of date pit powder to the polystyrene matrix. The theoretical modeling of the measured thermal conductivity and the scanning electron microscope (SEM) monographs supported the hypothesis of date pit agglomeration in the composite matrix. The prepared composites showed low thermal conductivity (0.0515-0.0562 W/m K at 25°C) and very low density (457-630 kg/m3), thus demonstrating their potential for use as a thermal insulator for building materials. In addition, replacing one-third of the classical construction wall content with DPP-polystyrene composite showed promise for constructive applications as a thermal insulator with 85% reduction in the overall thermal conductivity. Indeed, these properties are similar to those of other conventional insulating materials. This will lead to produce an inexpensive insulation material that exploits a common waste product in date fruit-producing countries.