Fibre reinforced polymer composites play an incredible role in almost all spheres of day to day life and the field of carbon composites is one of the prime research area in recent decade. Polymers are mostly reinforced with fibre or fillers to obtain better mechanical properties. The properties of the polymer composites can be improved largely by varying the type of filler/fibre materials and its volume percentage. Composites properties depend on the size, shape and other physical properties of the reinforcements. A relative easy way to improve the mechanical properties of a polymer is the addition of filler materials. In all particulate filled systems, the adhesion between the matrix and filler plays a significant role in determining the key properties such as strength and toughness. The mechanical properties of composites are also influenced by the filler’s nature, size and distribution profile, aspect ratio, volume fraction, the intrinsic adhesion between the surfaces of filler and polymer. In this paper, the effect of filler material on mechanical properties of E-Glass fibre reinforced polymer has been studied out by varying filler materials. For these study three different types of specimens were prepared, viz FRP without filler material, the FRP with 10 volume percentages of carbon black and the FRP with 10 volume percentage of Fly ash as filler material. The polyester composites were fabricated by hand-layup method. Mechanical properties of the specimens are analyzed using computerized Universal Testing Machine as per ASTM D 638 standards. The resulting behavioral patterns of the FRP with filler material are listed and compared to those of the FRP without filler material. Mechanical properties such as ultimate tensile strength, percentage of elongation, yield strength, Poisson’s ratio and percentage reduction in area were found out.