Summary: There is ongoing research interest in finding alternative sources of materials for composite manufacturing. Therefore, alternative non-wood based materials may play an important role in the forest product industry. Natural fibers have many advantages compared to synthetic fibers such as low density, lower cost, acceptable specific properties and being renewable and biodegradable. Natural fiber composites show high strength and stiffness, as well as good thermal and insulating properties. In this study, polymer matrix composites were manufactured using pine cone and marble waste and ATH powder as filler and polyester as matrix material with the casting method. Methyl ethyl ketone peroxide as hardener for cross-link network structure and cobalt naphthenate as accelerator were used to produce polyester matrix composites. Marble: ATH filler ratio was kept constant and polyester: filler (pine cone + marble + ATH) ratios were changed. Mechanical properties of composite materials were investigated and the final product tested to determine flexural strength, flexural modulus and hardness as well as some physical features such as bulk density, % total porosity and % open porosity. The experimental results showed that flexural strength and hardness of the composite materials decreased with the increase in pine cone: marble + ATH ratio.