In the last two decades, the level of investigation into low salinity water (LSW) flooding has sharply increased. LSW with adequate composition and salinity is injected into the reservoir, which changes the properties of the reservoir rock, thus improving oil recovery. However, for certain reservoirs there might be no improvement at all. This has led for further studies on what exactly governs the lack of improvement upon LSW injection in different reservoirs. Focus was placed on acidic and basic components present in crude oil. They are characterized by measuring total acid number (TAN) and total base number (TBN). This study investigates the wettability alteration of Berea sandstone rock with different crude oil acid and base numbers at specific LSW concentrations and compositions. For this purpose, the sessile drop method was used in specified times. Moreover, the experiments were conducted in two stages, which included crude oil A and B. The experimental results revealed that a significant change in wettability was experienced by the LSW composition of cations K+ and Na+ for the crude oil composition with lower acid number. © 2015, Japan Petroleum Institute. All rights reserved.