Dimensional stability, thermal, and water repellency are very important properties of wood. In this research, wood polymer nanocomposite (WPNC) has been prepared by impregnation of styrene acrylonitrile copolymer (SAN), gamma-trimethoxy silyl propyl methacrylate-modified TiO2 nanoparticles, nanoclay into simul ( L.) wood. The characterization of the composites was done by using Fourier transform infrared spectroscopy, X-ray diffractometry, and thermogravimetry. The resultant WPNC exhibited an improvement in water repellency, moisture resistance, dimensional stability, chemical resistance, hardness, and thermal stability. The maximum improvement in all the properties has been observed for the wood sample treated with SAN/TiO2 (0.5 %)/nanoclay (0.5 %).