Use of marine coral as a bio-filler in polymer composites is a new trend in many engineering applications like structural, coating, chemical resistance and electrical applications. In the present work, composite materials were prepared using epoxy matrix/cuttle bone powder (coralline calcium carbonate) at three different particle size and five different weight ratio. X- ray diffraction (XRD), thermogravimetry (TGA) and Fourier transforms infrared spectroscopy (FT-IR) spectra were used to analyze the crystalline nature, thermal degradation and composition of the cuttlebone, respectively. Tensile strength of the composites was examined and the morphological characteristics were studied by scanning electron microscopy (SEM). Results revealed that smaller particle size filler reinforced composites had better mechanical strength and uniform distribution.