Improving oil recovery in carbonate reservoirs using low salinity/smart water has been proven to be an efficient technique in the petroleum industry. It has been agreed in literature that a brine of salinity lower than that of formation water enhances the sweep efficiency by wettability alteration. However, the efficiency of the smart water depends on the chemical activity of the surface modifying agents known as the potential determining ions (PDIs); Ca2+, Mg2+ and SO4 2- , which is temperature dependent. Therefore, a comprehensive understanding of the effect of temperature on the PDIs during smart water injection is a key factor for the success of the process. This study aimed to investigate the effect of temperature on the activity of the PDIs as well as their interactions in modifying the wettability of oil-aged carbonate surfaces (calcite and dolomite). Temperatures of 25, 50, 75, 100 and 125 °C, representing global carbonate reservoir temperatures, were selected for the study. Wettability alteration was evaluated through contact angle (CA) measurement, while the effect of temperature on the surface charges at the fluid/rock interface was analyzed using zeta potential measurement. The concentrations of the PDIs before and after treatment were analyzed to gain an insight of the driving mechanism that led to wettability alteration towards a water-wet state. Results showed a decreasing trend of CA and a shift in wettability towards more water wetness for both mineralogies with temperature elevation, more significant at temperatures greater than 75 °C for all the three individual PDIs. However, this shift in wettability necessitates both high temperature and the presence of PDIs in the treating solution as no significant change in wettability was recorded after treatment of the carbonate surfaces with deionized water (DIW). Additionally, it was observed that Mg2+/SO4 2- combination had a better performance than Ca2+/SO4 2- combination at all temperatures for both carbonates. The strongest water-wet calcite surface resulted after treatment with smart water containing all the three PDIs at 125 °C, while the same was observed for dolomite after treatment with Mg2+/SO4 2- combination at the same conditions. Zeta potential results showed a charge reversal from negative to positive after treatment of the carbonate particles with all tested smart waters except the smart water containing only SO4 2- . A significant shift in surface charge was observed as temperature increases to 125 °C, which is in-line with CA results. Ions analysis of the smart water solutions after treatment with both carbonates revealed that the concentration of SO4 2- ions decreases with temperature, which is due to adsorption of the negatively charged ions on the rock surface. The final concentrations of Mg2+ and Ca2+ ions in the treating solution is however greater than its initial concentrations, which is a result of both dissolution and removal of the Ca/Mg- Carboxylate complexes from the surface, producing water-wet surfaces. Overall, the results confirm that an increase in temperature enhances the multi-ion exchange (MIE) between the ions in the solution and the carbonate surface. However, the interplay between the ions and the reaction kinetics not only depend on the temperature, but also on the surface mineralogy as well as the ion composition of the smart water.