The environmentally friendly vegetable oil-based waterborne polyurethane–organoclay nanocomposites have been successfully synthesized from castor oil polyols, isophorone diisocyanate and dimethylolpropionic acid. WAXD and TEM results showed that the addition of C30B containing a hydroxyl group led to the nearly exfoliated structures in WPUs. The thermal and mechanical properties of the nanocomposite films have been carefully investigated by FT-IR, DMTA, DSC, TGA, and tensile tests. As the C30B loading-level increased from 0 to 2%, the tensile strength and Young's modulus of the nanocomposites increased 16.7 to 27.9 MPa and from 22.3 to 134.8 MPa, respectively. The enhanced mechanical and thermal performance was primarily attributed to the formation of the strong interfacial interactions between filler and matrix. Morphological changes induced by the addition of clays were analyzed using rheological studies. This work produced new nanocomposites derived from castor oil polyols with a high-biomass content, and its high performance could contribute to a sustainable chemical industry.