Abstract: In the present study, the effect of moisture absorption on the properties of jute/flax-reinforced epoxy composite with coconut shell powder and eggshell powder as nanofillers was investigated.The nanocomposite samples were immersed in water for 6 mo then they were tested for various mech. properties in accordance with ASTM or ISO standardsSEM (SEM) was used to identify the potential cause of failure of the specimen after mech. tests.From the experimentations, it was found that jute/epoxy/coconuts shell powder, jute/epoxy/eggshell, flax/epoxy/coconut shell, and flax/epoxy/eggshell showed a reduction in their tensile strength of 29.29%, 24.89%, 20.17%, and 21.56% resp.They also showed reduced flexural strength of 19.72%, 18.46%, 22.63%, and 19.06% resp.Similarly, jute/epoxy/coconuts shell powder, jute/epoxy/eggshell, flax/epoxy/coconut shell, and flax/epoxy/eggshell showed a reduction in their impact strength of 11.35%, 6.88%, 9.25%, and 8.57% resp.But water immersion showed a pos. result on the surface roughness of the nanocomposite as the surface roughness of jute/epoxy/coconut shell and jute/epoxy/eggshell slightly improved by 12.5% and 14.28% resp.Morphol. anal. using SEM demonstrated fiber pullout, debonding, and voids due to moisture uptake which are responsible for weak interfacial adhesion between fiber and matrix which affects the overall performance of developed nanocomposites.