Hydrogen storage in the form of intermediate artificial fuels such as methanol is important for future chemical and energy applications, and the electrochemical regeneration of hydrogen from methanol is thermodynamically favorable compared to direct water splitting. However, CO produced from methanol oxidation can adsorb to H2‐evolution catalysts and drastically reduce activity. In this study, we explore the origins of CO immunity in Mo‐containing H2‐evolution catalysts. Unlike conventional catalysts such as Pt or Ni, Mo‐based catalysts display remarkable immunity to CO poisoning. The origin of this behavior in NiMo appears to arise from the apparent inability of CO to bind Mo under electrocatalytic conditions, with mechanistic consequences for the H2‐evolution reaction (HER) in these systems. This specific property of Mo‐based HER catalysts makes them ideal in environments where poisons might be present. Finding an antidote: Electrochemical methanol reforming to hydrogen is a simple, yet underdeveloped, approach for hydrogen storage; however, conventional metal catalysts are poisoned either by methanol crossover or by intermediate species (such as CO) from the corresponding methanol oxidation. Herein, the relative immunity of Mo‐based catalysts to CO is demonstrated, and the origins of this behavior are explored, with surprising implications for the general mechanism of H2 evolution on Mo‐based catalysts.