The effects of multiwall carbon nanotubes (MWCNT), nanolayered silicate (nanoclay), and trisilanolphenyl-functionalized polyhedral oligomeric silsesquioxane (PUSS) on the rheology and mechanical properties of an oligomeric polydiamine and the polyurea formed by its reaction with isocyanate were measured. The MWCNT and nanoclay increase the viscosity of the polydiamine and form a flocculated filler network at very low concentrations (<1%). This network imparts a strong strain-dependence to the dynamic modulus. These effects are absent with PUSS, which primarily affects the polyurea chemistry. The tensile modulus of the cured polyurea is higher for all three additives, with PUSS significantly toughening the material, provided adjustments to the stoichiometry are made. Published by Elsevier Ltd.