AbstractLignin was obtained from black liquor samples from soda-AQ pulping of oil palm empty fruit bunch (EFB) fiber. Oil palm EFB reinforced epoxy composite samples with varying lignin content of 15, 20, 25, and 30% as curing agent were prepared. The chemical structures of lignin were characterized by FT-IR, and CHN analysis. FT-IR and CHN analysis confirmed structural changes of epoxy resin after use of EFB-lignin as curing agent in epoxy resin. Thermal analysis of composites was carried out by thermogravimetric analysis (TGA). The TGA graphs showed that crosslinking of epoxy and lignin as curing agent may induce relatively high-chain rigidity in the polymer and may result in an enhanced thermal stability of the EFB/lignin-epoxy composite systems. The mechanical properties (tensile, flexural, and impact behavior) and physical properties (water absorption) of the composite samples were evaluated. Mechanical properties of epoxy composites cured with 25% lignin were found to be higher than that of the composite prepared from a commercial curing agent. Scanning electron micrographs showing tensile fracture of the composites showed evidence of good fiber–matrix interaction, induced by the curing agent.