The effects of glass fiber content and injection pressuree on the mechanical and viscoelastic properties of glass fiber-ABS composite were investigated. Fiber orientation, glass transition temperature, tensile modulus and storage modulus increased as glass fiber content increased. Tensile strength had the same propensity as tensile modulus except at high glass fiber content where its increase was negligible. It was found that fiber orientation had the maximum value at certain injection pressure and the pressure shifted toward higher pressure with the increase in glass fiber content. The same trends were observed for tensile and storage modulus. Some semi-empiricia1 equations were proposed to predict the tensile modulus by combining theoretical equations and fiber orientation parameters.