Currently enhanced oil recovery (EOR) technology is getting more attention by many countries since energy crises are getting worse and frightened. To improve oil recovery several techniques had been employed, one of them is wettability alteration during water flooding. In this research a novel hydrophobically associated polyacrylamide-SiO2 nanocomposite prepared by free radical emulsion copolymerization of hydrophilic and hydrophobic monomers had been prepared and characterized, where silica nanoparticles introduced through backbone structure of the polymer through Michael addition reactions to guarantee regular distribution of silica nanoparticles through polymer matrix. Chemical structure of the prepared nanocomposite was proven through different techniques such as Fourier transform infrared spectroscopy (FTIR), nuclear magnetic spectroscopy (H-1 NMR), scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD) while particle size and particle size distribution were characterized by dynamic light scattering (DLS) and thermal properties characterized by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Rheological and solution properties were evaluated at simulated reservoir conditions as a function of nanocomposite concentration and reservoir salinity, temperature and shear rate. The results showed that the nanocomposite exhibit favorable salt tolerance, temperature resistance, recoverable viscosity after shearing, reasonable thickening behavior and improved viscosity enhancement properties. Moreover, the nanocomposite capacity for interfacial tension reduction and oil production improvement was evaluated during flooding experiments through one dimensional sandstone packed model. Wettability alteration was evaluated by contact angle measurements through static sessile drop method, where the results indicate the novel nanocomposite ability for altering wettability of sandstone rock from oil-wet to water wet even at harsh reservoir conditions, so enhance oil recovery factor. (C) 2015 Elsevier Ltd. All rights reserved.