Nanocomposites containing nano-calcium carbonate (nano-CaCO₃) in the range of 0.25–1.5% (w/w) were prepared via in situ polymerization of urethane methacrylate pre-polymer derived from poly(ethylene glycol) (PEG 400), polymeric diphenylmethane diisocyanate and 2-hydroxyethyl methacrylate. Incorporation of nano-CaCO₃ into poly (urethane methacrylate) matrix was confirmed by Fourier transform infrared spectroscopy and wide-angle x-ray diffraction studies. Density studies indicated that nanocomposites containing 0.75 wt% nano-CaCO₃ had more condensed microstructure. Tensile strength, abrasion resistance, heat deflection temperature and shore hardness of nanocomposites were found to be higher than that of pristine polymer. Impact strength decreased with an increase in the nano-CaCO₃ content. Thermal studies indicated single-step degradation under a nitrogen atmosphere. Scanning electron microscopy studies confirmed the uniform distribution of nano-CaCO₃ at lower loading of nano-CaCO₃ and microcracking occurred during wearing.