In this study, the surface of silica nanoparticles (NPs) synthesized using the Stöber method was modified with 3-aminopropyltriethoxysilane and hydrolyzed polyacrylamide (HPAM). The surface modification of the silica NPs was confirmed by Fourier transform infrared spectroscopy, field emission gun scanning electron microscopy, and thermogravimetric analysis. The characteristics of the nanopolymer sol were evaluated using rheology, viscosity retention ratio, interfacial tension, and contact angle measurements. The core flooding experiments were performed at 56 °C using Berea core plugs with Klinkenberg permeabilities of 450 and 478 mD and a porosity of ∼21%. The nanopolymer sol was prepared in injection brine (0.24 wt % TDS) with 550 ppm of the nanohybrid, while the polymer solution was prepared with 750 ppm of HPAM. The displaced fluid was dead oil with a viscosity of 60 cP (@56 °C and 7.3 s–1). The results show that the nanopolymer sol reduces the capillary forces and increases the viscous forces compared to the HPAM solution. These improved properties of the nanopolymer sol were suitable for increasing the cumulative oil recovery in 2.2% OOIP in comparison with the HPAM solution at a lower concentration.