Smart water flooding, as a popular method to change the wettability of carbonate rocks, is one of the interesting and challenging issues in reservoir engineering. In addition, the recent studies show that nanoparticles have a great potential for application in EOR processes. However, little research has been conducted on the use of smart water with nanoparticles in enhanced oil recovery. In this study, stability, contact angle and IFT measurements and multi-step core flooding tests were designed to investigate the effect of the ionic composition of smart water containing SO42− and Ca2+ ions in the presence of nanofluid on EOR processes. The amine/organosiloxane@Al2O3/SiO2 (AOAS) nanocomposite previously synthesized using co-precipitation-hydrothermal method has been used here. However, for the first time the application of this nanocomposite along with smart water has been studied in this research. Results show that by increasing the concentrations of calcium and sulfate ions in smart water, oil recovery is improved by 9% and 10%, respectively, compared to seawater. In addition, the use of smart water and nanofluids simultaneously is very effective on increasing oil recovery. Finally, the best performance was observed in smart water containing two times of sulfate ions concentration (SW2S) with nanofluids, showing increased efficiency of about 7.5%.