AbstractVarious fillers have been introduced into poly (butylene adipate‐co‐terephthalate) (PBAT) to produce biodegradable plastics with enhanced performance. Recently, lignin nanoparticles have attracted much attention as fillers because they exhibit good compatibility with plastics and a mechanical enhancement effect. In this study, maleic anhydride‐modified ligninsulfonate nanoparticles (MLSs) were prepared and incorporated into PBAT by melt blending. Scanning electron microscopy images showed that MLSs were well dispersed in PBAT at a 10% incorporation ratio. Mechanical measurement results indicated that the incorporation of MLSs in PBAT simultaneously enhanced the tensile strength, elongation at break, tensile modulus, and flexural modulus. Dynamic rheological measurement indicated that the viscosity and modulus decreased with the incorporation of MLSs, revealing relatively low compatibility between MLSs and PBAT in a melting state.