To better understand the electrochemistry of nickel electrowinning from nickel chloride solutions at the cathode-electrolyte interface, the cathode surface pH was measured using a flat-bottom combination glass pH electrode and a 500 mesh nickel-plated gold gauze as cathode. The cell was a modification of that designed by Romankiw and coworkers. The pH electrode was positioned at the back of, and in direct contact with, the gauze cathode. As expected, the cathode surface pH was always higher than the pH in the bulk electrolyte, and if the current density was sufficiently large, it could cause the precipitation of insoluble Ni(OH)(2(5)) on the cathode surface. Lower bulk pH, higher nickel concentration, higher temperature, and the additions of H3BO3 and NH4Cl effectively suppressed the rise of the cathode surface pH. The results provide further evidence of the buffering action of H3BO3 and NH4Cl and of the enhancement of nickel deposition by H3BO3 At current densities less than 240 A m(-2) additions of NaCl and Na2SO4 suppressed the rise of the cathode surface pH but to a much smaller degree.