Concerns regarding environmental deterioration as well as issues regarding the sustainability of fast depleting petroleum resources used to make conventional plastics have forced the scientific community to focus on developing and manufacturing new and novel ‘green’ materials that are fully biodegradable and derived from renewable, plant-based resources. In the present study a non-edible starch, extracted from avocado (Persea americana) seed starch (AVS), a waste product of avocado processing, was developed for fabricating ‘green’ composites. AVS was crosslinked using a green crosslinker, 1,2,3,4-butane tetracarboxylic acid (BTCA), and a catalyst, sodium hypophosphite (SHP), to prepare a rigid thermoset resin with improved water resistance. Two cellulose based reinforcements, micro-fibrillated cellulose (MFC) with average diameter of 50 nm and velvet leaf (a common weed) stem derived microfibers (VLF) with average diameters of 12 μm were used to fabricate green composites. Properties of these green composites were fully characterized and compared with different compositions. In addition, advanced ‘green’ composites with excellent mechanical properties were fabricated by combining liquid crystalline cellulose (LCC) fibers with MFC blended AVS (MFC/AVS) resin. LCC fibers were modified using a combination of alkali and heat treatments to further improve their tensile strength from 1.5 GPa to over 1.9 GPa. The advanced green composites prepared by simple hand layup showed average tensile strength of 380 MPa and Young’s modulus of 25 GPa with only 40% of LCC fibers by volume. This study clearly demonstrates the potential of AVS based green composites for industrial applications such as automotive, packaging, construction and others.