Electrocatalytic hydrogenation (ECH) of guaiacol was performed in a stirred slurry electrochemical reactor (SSER) using 5 wt % Pt/C catalyst in the cathode compartment. Different pairs of acid (H2SO4), neutral (NaCl), and alkaline (NaOH) catholyte–anolyte combinations separated by a Nafion® 117 cation exchange membrane, were investigated by galvanostatic and potentiostatic electrolysis to probe the electrolyte and proton concentration effect on guaiacol conversion, product distribution, and Faradaic efficiency. The acid–acid and neutral–acid pairs were found to be the most effective. In the case of the neutral–acid pair, proton diffusion and migration through the membrane from the anolyte to the catholyte supplies the protons required for ECH. Typically, the two major hydrogenation products were cyclohexanol and 2‐methoxycyclohexanol. However, ECH at constant cathode superficial current density (−182 mA cm−2) and higher temperature (i.e., 60 °C) favored a pathway leading mainly to cyclohexanone. The guaiacol conversion routes were affected by temperature‐ and cathode potential‐dependent surface coverage of adsorbed hydrogen radicals generated through electroreduction of protons.