Abstract In this paper, we investigated the effect of fiber content, interfacial compatibilization, and manufacturing process on the mechanical properties (tensile, impact and creep) of sisal fiber (SF) reinforced high-density polyethylene (HDPE) composites. The increase of fiber content and interfacial compatibilization with maleic anhydride grafted HDPE (MAPE) were found to improve the mechanical properties of the composites. Compared with simultaneous blending, a pre-impregnation process with the compatibilizer, namely MAPE, improved the interfacial bonding between the fibers and the matrix, which in turn improved the mechanical properties of the composites. The General Power-Law equation was used to model the creep behavior of the composites. The identified material parameters based on the creep data were used to predict the creep-recovery behavior of the composites, and good agreement was achieved between the predicted and experimental creep-recovery responses.