Among many Enhanced Oil Recovery (EOR) methods, chemical flooding for wettability alteration of carbonate oil-wet rock is one of the most noticeable methods amid researchers. However, several crucial aspects concerning wettability alteration are still unknown and unanswered to date. Understanding the ionic composition of brine is a very important subject to which numerous studies are being dedicated, with the objective of determining the role of brine and its composition on wettability alteration, particularly its effects on EOR. The objectives of this research work is the investigation of the effects of different brine ions (Ca2+, Mg2+ and SO4 2-) on wettability alteration of oil-wet carbonate rocks while using cationic surfactant flooding Dodecyl Trimethyl Ammonium Bromide (DTAB). Results showed that the presence of SO4 2-is crucial and can improve DTAB efficiency. Contact angle maximum change is 62o to 19o with concentration of Na2SO4 equal to 6 g/l. © 2017 Trans Tech Publications, Switzerland.