In this study, both untreated and treated rice husk fibers with a silane coupling agent are incorporated with epoxy resin to prepare particleboard composites. The effect of different ratios of nanoclay 5%, 10%, 15%, and 20% (by the weight of the polymer) on the physicomechanical properties of the prepared particleboard composites is investigated. The results show that the flexural, and impact strengths as a function of mechanical properties getting better with increasing nanoclay content up to 10%. While the addition of nanoclay to the samples decreases the water absorption percentage. This decrease is almost constant with nanoclay (%). In addition, the effect of different doses of gamma-irradiation on the properties of both untreated and treated rice husk-epoxy particleboard composites that containing 10% of nanoclay is also discussed. The results show that the irradiated specimens at a dose of 10kGy achieved a good enhancement in mechanical properties whereas the water absorption percentage as a physical property decreases at a dose of 10kGy and starts to increase with increasing gamma irradiation doses. TGA, and SEM are carried out to confirm the data obtained.