Polyurethane foam was fabricated from polymeric diphenylmethane diisocyanate (pMDI) and soy-based polyol. Nanoclay Cloisite 30B was incorporated into the foam systems to improve their thermal stabilities and mechanical properties. Neat polyurethane was used as a control. Soy-based polyurethane foams with 0.5-3 parts per hundred of polyols by weight (php) of nanoclay were prepared. The distribution of nanoclay in the composites was analyzed by X-ray diffraction (XRD), and the morphology of the composites was analyzed through scanning electron microscopy (SEM). The thermal properties were evaluated through dynamic mechanical thermal analysis (DMTA). Compression and three-point bending tests were conducted on the composites. The densities of nanoclay soy-based polyurethane foams were higher than that of the neat soy-based polyurethane foam. At a loading of 0.5 php nanoclay, the compressive, flexural strength, and modulus of the soy-based polyurethane foam were increased by 98%, 26%, 22%, and 65%, respectively, as compared to those of the neat soy-based polyurethane foam. The storage modulus of the soy-based polyurethane foam was improved by the incorporation of nanoclay. The glass transition temperature of the foam was increased as the nanoclay loading was increased. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 1857-1863, 2011