Polymer plays a vital role in chemical-enhanced oil recovery (CEOR) for additional oil production. Still, it has some limitations such as lower stability at a higher temperature, higher salinity, and higher shear rate, which affects the efficiency of the system. Nanoparticles have the ability to strengthen the stability of polymer solutions against reservoir conditions and so, an attempt has been taken to investigate the role of nanoparticles in stabilizing the polymer for better performance in an oil recovery process. In this research, partially hydrolyzed polyacrylamide (HPAM) as a polymer and silica nanoparticles and alumina nanoparticles were used to investigate the stability of polymer solutions. The thermophysical properties of the nanoparticles have been evaluated with the help of a thermogravimetry analyzer, while the particle sizes of nano-silica and nano-alumina have been assessed with the use of a particle size analyzer. The effect of temperature, shear rate, and salinity has been tested over the viscosity of the polymeric solution without nanoparticles and with nanoparticles using Anton Paar rheometer. The impact of concentrations of nanoparticles (0.05–0.25 wt%) and concentrations of HPAM (1000–3000 ppm) was evaluated over the temperature variation (30–70 °C), shear rate variation (1–200 s−1), and salinity (10,000 ppm) conditions. Particle size analysis indicates that the size range of the silica and alumina lies within the 400–500 nm scale. The results indicate a significant improvement in the rheology of the polymer solution over given critical conditions after adding the nanoparticles.