Replacing oil from small pores of tight rocks relies on altering the rock wettability with the injected fracturing fluid. Among different types of wettability-alteration surfactants, liquid nanofluid (LNF) has less adsorption loss during transport in the porous media and can efficiently alter the rock wettability; both make LNF a promising candidate to enhance oil recovery from tight reservoirs. In this study, a 2.5-D visualized micromodel with micro-sized pore throats is applied to elucidate the impacts of wettability alteration and spontaneous imbibition on oil-water flow in the porous media. Results provide direct evidence that the concentration of LNF changes wettability alteration rate and interfacial tension, and thus influencing the displacing rate of water into the originally oil-wet pores. This helps to optimize LNF usage in the fracturing fluid for enhanced oil recovery from tight rocks.