Nipa palm fibres were used in producing fibre boards with different mixtures of waste HDPE fibres. Density, swelling thickness and water absorption of the boards were determined and compared to know the combination that would yield the best quality. The relationship between the densities of boards produced and their ability to absorb water was also established. The significance of the results implies that the boards have special water resistant property, a feature that makes them suitable for use in areas of high humidity or occasional wetness. It is also noted that as more plastic waste is incorporated into Nipa fibres, the less density impacted on the particle boards and, hence, more water is absorbed.