In this study, tensile and fatigue behavior of glass fiber-reinforced (MAT-8)/polyester automotive composite was investigated experimentally. The composite used in this study consists of polyester, fiber and gelcoats. The fiber contents were kept constant at 37 wt% during the tests. But, polyester and gelcoat contents were changed. The tests were conducted at five different MAT-8 thicknesses. It is clearly shown that polyester content is the only determinative factor for fatigue strength, while both polyester and gelcoat contents are effective for tensile strength. According to the results, optimum tensile strength was achieved, while fiber ratio was constant in the specific mixing of polyester and gelcoats. It is thought that the combination of 52.14 wt% polyester and 9.75 wt% gelcoats can be a preferableway for designs requiring the best tensile and fatigue strength properties at the same time.