Titanate whisker‐reinforced polypropylene composites were prepared in a twin‐screw extruder followed by injection molding. The whiskers were surface treated with tetrabutyl orthotitanate prior to blending. The static and dynamic mechanical properties, impact strength, and thermal properties of the composites were investigated. Static tensile measurements showed that the tensile strength and Young's modulus of the composites increased with increasing whisker content. However, the Izod impact tests indicated that the impact strength of longitudinal samples remained unchanged with the addition of whisker up to 10 wt %. Thereafter, it shows a continuous decrease with increasing whisker content. The thermogravimetric and dynamic mechanical tests demonstrated that the heat‐resistance and thermooxidative stability for the composites also increased with increasing whisker content. Scanning electron microscopic observations revealed that the whiskers within the composites were oriented uniformly. The experimental data were compared with the well established mechanical models to evaluate the reinforcing efficiency. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 431–439, 1998