Combined enhanced oil recovery (EOR) methods have been proposed to benefit from several simultaneous mechanisms. The application of nanoparticles and carbonated water have been studied in recent years. In this study, Axisymmetric Drop Shape Analysis (ADSA) was applied to investigate the ability of a hybrid technique – i.e., the simultaneous use of TiO2, MgO, and γ-Al2O3 nanoparticles and carbonated formation water as an available water source in reducing interfacial tension (IFT) as a main EOR mechanism. To achieve this goal, the initial and 10 diluted samples of formation water were selected as the base fluids. The nanoparticles were dispersed at concentrations of 500 and 1000 ppm in the base fluids and were stabilized using ultrasonic waves. Carbon dioxide was applied to the system at temperatures of 40, 60, and 80 °C and pressures of 0.10, 6.89, and 13.79 MPa. In this way, the effects of salinity, nanoparticle concentration, temperature, and pressure were investigated on IFT values in carbonated nanofluid injection. The results show that the combination of these two methods has a significant effect on the reduction of IFT. In addition, the IFT between carbonated nano-fluids and crude oil shows a direct relationship with the temperature and salinity of the base fluid and reverse relationship with the concentration of nanoparticles and the pressure.