This paper describes preparation of the bio-based polyurethanes from the rapeseed oil polyols, solution incorporation of three diverse nanoclay additives and investigation of the mechanical property for the prepared materials. Nanoclays are based on montmorillonite organically modified with different content of alkylamonium compounds. The results of hardness and tensile properties investigation for polyurethane / montmorillonite nanocomposites are presented. The influence of the nanoclay content on the hardness, tension elastic modulus, tensile strength, and strain at break of the nanocomposites is determined. The polyurethane nanocomposites show an increase in the mechanical properties due to the incorporation of rigid inorganic nanoparticles. Analysis of the property-concentration relationships considers the role of agglomeration and interphase phenomena on the final values of nanocomposite mechanical characteristics.