This paper experimentally investigates the effect of prestressing levels on the tensile properties of prestressed glass fiber reinforced polyester laminates. A test rig was developed to apply and maintain controlled tensile stress applied to the glass fibers during molding, creating prestressed laminates. Five different prestressing levels of 10%, 20%, 30%, 40%, and 50% were studied. Tensile tests, following ASTM D3039, were conducted on standard specimens with a 29% fiber volume fraction to evaluate the influence of prestressing level on tensile strength, modulus, and energy absorption. Results showed that prestressing significantly enhances the tensile characteristics of the laminates. Even at the lowest prestressing level of 10%, there were notable improvements of 31%, 21%, and 39% in tensile strength, modulus, and energy absorption, respectively. An optimal prestressing level of approximately 28% yielded the highest gains, with substantial increases of 46.5% in tensile strength, 39% in modulus, and 59.5% in tensile energy absorption. Exceeding this level resulted in a decrease in performance, although properties remained superior to non-prestressed laminates. Empirical equations were developed to represent the relationships between the prestressing level and the studied tensile characteristics. These findings suggest that prestressing is a promising method for improving the tensile characteristics of glass fiber reinforced polyester without increasing weight or dimensions. This makes it a valuable material for applications requiring high strength and lightweight properties, such as building facades, automotive body panels, aircraft fuselage panels, marine boat hulls, and wind turbine blades.