Abstract Development and evaluation of new bio-based sustainable plastics to replace the petroleum-based materials in different industrial applications has both environmental and economic benefits. Bio-based polymers can be widely used in biomedical and agriculture applications due to their excellent biodegradability and biocompatibility. Soy protein is a natural material that can be isolated from soybean, which is a major agricultural crop in the U.S. The viability of soybean-based polymers and composites is questioned due to their high-water absorption and poor mechanical properties. There have been many environmentally friendly attempts to improve the properties of soybean polymers as soybeans and their extracts are widely available worldwide. Soy protein, hulls, and oils all find use in the development of different biodegradable polymers. While the development looks promising, there is still more work to do to make the soybean polymers useful and economically viable. Blending soy protein with other biodegradable polymers, such as polylactide (PLA) and polyurethane dispersion is a valid approach to improve the mechanical properties of soy protein and reduce its water sensitivity.