Although nacre (mother of pearl) is composed of mostly brittle aragonite (CaCO3) nanoplatelets and little amount of biopolymers, it shows superior mechanical properties like tensile strength and fracture toughness because of its hierarchical brick-and-mortar structures from molecular to macro levels. In this research, we extracted cellulose nanofiber from tunicate and fabricated bio-friendly composites, montmorillonite (MMT)-cellulose nanofiber (CNF) nanocomposites, by a simple filtration process to mimic nacre structure for enhancing its mechanical performances. We optimized the properties of MMT/CNF composites by varying MMT/CNF ratio, which was characterized by a scanning electron microscope (SEM), an X-ray diffraction (XRD), and a Fourier transform infrared spectroscopy (FT-IR). Also, relatively high toughness and strength were obtained by measuring in a tensile tester. These results suggest that our bio-friendly MMT-CNF composites have a potential replacement of commercial polymers.