The effect of various cow bone particle sizes and different volume fractions on the fracture behavior of a cow rib bones-reinforced polyester material is demonstrated in this paper. This study is useful to researchers whose interests lie in the growth of bone technology. A polyester matrix composite was manufactured using four various cow bone particles sizes (600 μm, 850 μm, 1180 μm, and 1700 μm) as reinforcement. Two mechanical (Tensile and Flexural) tests were performed. For each particle size, the samples were prepared at three different volume fractions (35%, 45%, and 55%). The results detected that the tensile and flexural loads increase with the decrease in the volume fraction of the particles and increase with the decrease of the particle sizes as well.