The aim of this paper is to study the influence of fiber content and surface treatments on morphology, dielectric and mechanical properties of date stones (DS) fiber reinforced polyvinylchloride (PVC) composites. Different fiber loadings were added to PVC matrix (ranging from 5-20 wt %). The obtained results reveal that both methods, i.e. chemical treatment of DSs with acetic anhydride and heat treatment, improved the interactions between the two composite components (DSs and PVC) and promoted better dispersion of the filler within the matrix. The ductility which was measured as percentage of elongation at break, decreases as filler loading increases, the same behavior of strength at break was observed. Whereas, the addition of both heat and chemical treated fibers to the polyvinylchloride improve slightly these properties. With increasing the filler content, dielectric constant, dissipation factor and conductivity increased, which was mainly due to the motion of dipolar groups of the interfacial polarization occurring within the composites. However, surface modification of fibers resulted in a decrease of the dielectric properties.