AbstractA natural polymer composite (NPC) was developed from a palm decanter cake (OPDC), and its properties were determined. Oil palm decanter cake natural polymer composite (OPDC-NPC) samples were produced at different ratios of polypropylene (PP) and OPDC before being subjected to flexural, tensile, and water absorption tests. The results showed that by increasing the OPDC content from 5 to 15%, the rigidity as represented by the flexural strength and tensile strength increased from 29 to 43 MPa and 12 to 21 MPa, respectively. However, the flexural modulus decreased from 2230 to 1365 MPa and the water absorption rate increased from 0.16 to 0.44% because of the hydrophilic nature of the OPDC material. The rigidity of OPDC-NPC can thus be improved by increasing the OPDC content from 5 to 15%.