In order to ensure thermal comfort and reduce energy consumption, a new composite based on Portland cement and date palm fiber was studied in this work. Our main objective is to study the possibility of integrating and using this new material as a thermal insulation material in the exterior coatings of buildings. Several composites were prepared for different weight concentrations (from 0% to 5%) of date palm fibers. The studied materials were analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). In addition, the hot wire method was used to measure thermo-physical properties. The results show that the addition of fibers has no effect on the chemical composition of the matrix, as shown by FTIR and XRD analyzes which proves the chemical stability. The results of the TGA analysis indicate that the inclusion of date palm fibers has an effect on the thermal characteristics of the matrix. The SEM analysis shows that there is good adhesion between the Portland cement and the plant fibers used and that the date palm fibers are well incorporated into the matrix, the SEM images also showed that the inclusion of the fibers increases the porosity. In addition, the results showed that the addition of the fibers of date palm a marked decrease in thermal conductivity, which makes the material insulating. Thus, the use of fibers in cement seems to be a promising option that allows it to be applied as a thermal coating material in buildings.