Wettability alteration is one of the most important methods for oil recovery from sandstone and carbonate reservoirs. The effects of salinity, pH, temperature, and chemicals such as surfactants and fatty acids on the alteration of the wettability were described in previous studies. In recent years, attention has been directed to nanoparticles as a wettability alteration agent. The effect of some nanoparticles on the wettability alteration and oil recovery of sandstone and a few carbonate reservoir rocks have been investigated in several works. In this study, the effect of γ-Al2O3 on the wettability alteration of one of the Iran carbonate reservoirs is presented. The results show that the adsorption of γ-Al2O3 nanoparticles on the calcite surface changes the wettability from oil-wet to water-wet. At a γ- Al2O3 nanofluid concentration of 0.5 wt.%, the maximum change in contact angle was observed. It was observed that the oil recovery increased by 11.25% when 0.5 wt.% γ-Al2O3 nanofluid was injected into the core sample in a tertiary mode. This work illustrates the successful application of gamma alumina nanoparticle in enhancing oil recovery in carbonate rocks through the wettability alteration of rock surfaces.