More than 50% of oil remains in reservoirs after primary and secondary recovery processes. Consequently, methods of enhanced oil recovery (EOR) should be applied for more recovery from these reservoirs. In this study the ability of hydrophobic nanoparticles of sio₂ in EOR process through carbonate rock samples is studied. By employing hydrophobic nanosilica, we can lower interfacial tension between oil and nanofluid and then reduce the mobility ratio between oil and nanofluid in carbonate reservoirs; however, nanosilica can increase the viscosity of water exponentially. To evaluate this goal, core displacement experiment for carbonate core is conducted. These experiments are performed on the carbonate samples saturated with oil and brine that had got injected with nanosilica with six different concentrations. Investigating the outcomes shows that by rising nanoparticle concentration, the IFT between water and oil phases decreases and yields in decrease the mobility ratio between oil and nanofluid. For this, we measure the recovery level in different states of using 0.05, 0.1, 0.1, 0.15, 0.3, 0.6, 1.0, and 0 concentration of the nanoparticle. The outcomes achieved from our experiments reveals that employing hydrophobic nanosilica could increases the oil recovery factor.