Electrolysis‐assisted nitrate (NO₃⁻) reduction is a promising approach for its conversion to harmless N₂ from waste, ground, and drinking water due to the possible process simplicity by in‐situ generation of H₂/H/H⁺ by water electrolysis and to the flexibility given by tunable redox potential of electrodes. This work explores the use of a polymer electrolyte membrane (PEM) electrochemical cell for electrolysis‐assisted nitrate reduction using SnO₂‐supported metals as the active cathode catalysts. Effects of operation modes and catalyst materials on nitrate conversion and product selectivity were studied. The major challenge of product selectivity, namely complete suppression of nitrite (NO₂⁻) and ammonium (NH₄⁺) ion formation, was tackled by combining with simultaneous photocatalytic oxidation to drive the overall reaction towards N₂ formation.