The pH of CO2-saturated brines is of importance in geological carbon storage utilizing saline aquifers as it is a key variable controlling fluid-mineral chemical reactions that affect CO2 storage capacity and security. In this paper, we report experimental measurements of the pH of CO2-saturated aqueous KCl solutions carried out using high-pressure glass and ZrO2 pH electrodes, coupled with a Ag/AgCl reference electrode, at a temperatures from (298 to 423 K) and at pressure between (0.2 and 13.5) MPa. The results are in good agreement with values predicted using the Pitzer model with the McInnes convention as implemented in the PHREEQC geochemical simulator software. The pH of CO2-saturated KCl solutions decreases with increasing partial pressure of CO2 and increases with increasing temperature. Increasing the molality of the KCl solutions tends to lower the pH but not as rapidly as is the case the NaCl.