This paper presents the effect of accelerated salt spray (fog) exposure on commercially glass fiber reinforced polyester composite to determine the durability of the material. Aging behavior after exposure in the salt-spray environment was studied by mechanical properties i.e. flexural stress and flexural modulus. The accelerated salt spray exposure was conducted by Copper-Accelerated Acetic Acid Salt Spray (CASS) Test according to ASTM B368. The CASS exposure was carried out for 120 hours and observed every 24 hours. The flexural modulus results tend to be constant up to 4 days and more significant change on 5th day of measurement. Furthermore, the morphology of specimens investigated by a Scanning Electron Microscopy (SEM). The SEM results also showed that only scratch occurred on the surface of the specimens test. The longer of the CASS exposure time, the higher the number of scratches. From this study, it could be concluded that Glass Fiber Reinforced Polyester Composite has slightly damage for 120 hours CASS test exposure.