In this study, a series of cast polyamide-based composite materials were produced by injection molding process. In the production of composite materials, cast polyamide and short glass fiber were used as matrix and reinforcement materials, respectively. The specimens obtained from composite materials having different fiber content were tested to determine tensile and impact strength, modulus of elasticity, tensile elongation and density of composites. In addition, scanning electron microscopic studies were carried out on the fracture surfaces of impact test specimens. It was observed that mechanical properties of composites such as tensile strength and modulus of elasticity increased when the fiber volume content is increased up to 35%. However, these properties decreased at the fiber content higher than that of 35%. Moreover, tensile elongation and impact energy values were decreased when the fiber content was increased. In addition, the fiber efficiency factor increased with the increasing fiber content up to 35%, and after this point, it decreased with the increasing fiber content. On the other hand, it was observed that the fiber efficiency factor for modulus of elasticity was higher than that of the tensile strength. Consequently, it was observed that adding short glass fiber up to 35% was an effective method to improve mechanical properties of cast polyamide-based composites.