The measurement of pH at high temperatures is often desirable for the control and monitoring of industrial processes. A typical example is pressure acid leaching (PAL) of laterite ores, which is conducted in autoclaves at a temperature around 250°C, to extract nickel and cobalt. In this paper, the implementation of a flow-through electrochemical cell with an yttria-stabilized zirconia (YSZ) sensor for in-situ measurement of pH in PAL process solutions is discussed. Various laterite ore samples were leached at different H 2SO4 concentrations. The PAL solutions were filtered at temperature and then passed through the electrochemical cell. Overall, good agreement was found between the measured pH values and those theoretically predicted using the OLI Systems® software package calibrated independently based on solubility measurements. This fact suggests that the flow-through electrochemical cell can be satisfactorily used for hydrometallurgical process research and development.