Potassium titanate (K2Ti6O13) whisker treated with tetrabutyl orthotitanate was used to improve the mechanical and thermal properties of the poly(acrylonitrile-butadiene-styrene) (ABS) copolymer. The composites were prepared in a twin-screw extruder followed by injection molding. Static tensile measurements showed that both the modulus and breaking stress of ABS/K2Ti6O13 composites increase considerably with increasing whisker content; the strain at break of ABS was almost unaffected by the incorporation of a whisker content up to 15 wt %. Izod impact tests indicated that the composites showed a decrease in the impact strength with increasing whiskers content. Thermogravimetric analysis showed that the K2Ti6O13 whisker additions have little effect on the thermooxidative stability of ABS. Scanning electron microscopic observations revealed that the whiskers were aligned along the melt-flow direction in the thin surface layer, whereas the whiskers were oriented randomly as well as perpendicular to the injection direction in the thick core region of the composites. The Tsai-Halpin equation was used to evaluate the moduli of the ABS/K2Ti6O13 composites. The theoretical calculations generally correlated well with the experiment data by assuming K2Ti6O13 whiskers to have an aspect ratio of 12.