Lignin-containing cellulosic nanofibrils (LCNF) were extracted from residual oil palm empty fruit bunches (EFB), an abundant but underutilized bioresource, by using a set of sulfur-free fractionation methods. The various types of isolated LCNF were used to reinforce starch-based biofoams. The incorporation of LCNF achieved remarkable increases, by a factor of 44 and 66, of the Young's modulus and yield stress in compression mode, respectively. In addition, owing to the relatively lower hydrophilicity of residual lignin, water sorption by the composite biofoams was reduced with LCNF loading. The starch/LCNF nanocomposite biofoams displayed mechanical properties similar to those of polystyrene foams and therefore can potentially represent a sustainable and green alternative for packaging and insulation materials.