Spinel oxides, especially Co₃O₄, have been considered as ideal electrocatalysts for electrocatalytic nitrate reduction reaction (e-NO₃RR). However, their application in e-NO₃RR is still limited because of relatively low activity and selectivity under high potential. Herein, we present that the incorporation of manganese (Mn) into the Co₃O₄ lattice can achieve the high activity and selectivity in e-NO₃RR. The Mn-incorporated Co₃O₄ nanotubes show a remarkable e-NO₃RR activity with a high ammonia yield rate of 35 mg h⁻¹ cm⁻² and excellent selectivity with a Faraday efficiency for ammonia up to 99.5% in neutral media, which are much better than those of transition-metal oxides. Our calculations further show that the replacement of Co by Mn can tune the adsorption behavior of intermediates, and thus reduces the limiting potential of e-NO₃RR. We believe that the findings provide an insightful guidance to engineer the spinel oxides for enhanced performance towards ideal products.