Due to the growing concern over the depletion of the global crude oil stock and environmental issues, the replacement of petroleum-based polymers with environmentally benign alternatives derived from renewable resources has attracted great attention. In this study, a variety of bio-based polyurethanes were effectively made from polyols produced by the thiol-ene reaction of vegetable oils. Crude oils were hydroxylated with performic acid, created on-site by the reaction of hydrogen peroxide and formic acid to create the polyol. The resulting polyols were then used in the synthesis of polyurethanes. The characteristics of these bio-based polyurethanes can be determined by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and tensile testing to understand their mechanical properties. Additionally, the mechanical and thermal properties of these plastics were enhanced by incorporating reinforcing materials such as cellulose nanofibers. These environmentally friendly polyurethanes, synthesized from various vegetable oils, exhibit potential for diverse applications, including packaging, construction, automotive, and biomedical fields, demonstrating their versatility and sustainability.