Abstract: Nanoclay-epoxy composites have been applied widely since they have excellent properties which resulted from the incorporation of the nanoclay material in epoxy matrix. However, the improved properties can degrade by presence of water in the epoxy matrix, leading to limitation of service life of the material. Diffusion of water having 40 and 60°C in the nanoclay-epoxy composites made by direct mixing process was investigated through immersion test. The strength of the materials was also measured by using the three point bending test. The results showed that the two-stage diffusion process occurred when the composites immersed in water at 60°C whereas the Fickian diffusion mode was observed in case of water at 40°C. The saturation and the diffusion rate are influenced by organoclay loading and by temperature. Increase of clay loading resulted in an increase of the water saturation and reduction of diffusion rate of water. The results also showed the significant influence of temperature on water absorption of the composites. Water saturation, increased about 20% and water diffusion rate was 5 time-higher when temperature of water shifted from 40 to 60°C. Investigation of flexural strength was carried out by use of the three point bending test. The results showed decrease of flexural strength with an increase of clay loading for the composites. However, there was no significant change of flexural strength during the immersion. Results for the neat resin showed to the contrary.