The effect of coupling agent and fi ber content on physical and mechanical properties of a lignocellulosic materialthermoplastic polymer composite was examined. Using poplar fi ber as the reinforcing fi ller, polypropylene as the thermoplastic matrix polymer, and maleated polypropylene as the coupling agent, reinforced composites were prepared. In the sample preparation, three levels of fi ber loading (55, 70 and 85 wt.%) and three levels of coupling agent content (0, 2 and 4 wt.%) were used. The mechanical strengths of the composites slightly increased as the fi ber loading increased, but the physicomechanical properties were signifi cantly improved with the addition of the coupling agent.