Abstract: In this study, oil palm (Elaeis guineensis) empty fruit bunch (EFB) fiber was incorporated with glass fiber in polyester composite by wet-lay up process. Mechanical and physical properties of composites were evaluated. Flexural strength and density decreased with increasing EFB fiber but the addition of EFB fiber volume fraction around 40-70% increases flexural strength of polyester resin, by about 350%. The addition of 40% volume fraction EFB fiber resulted in the similar flexural strength with glass fiber/polyester composites but showed lower density. This suggests that EFB fiber have a potential to replace glass in many applications that do not require very high load bearing capabilities. Water absorption and thickness swelling ability tend to increase with the increasing EFB fiber addition. Fiber length showed no significant effect on the flexural strength and density of composites, but shorter EFB specimen is able to absorb water and change the dimension of composites higher than the longer fiber.