Cold-rolled Ni3Al foils were found to be spontaneously activated up to a high level during methanol decomposition, forming Ni particles on the foil surface. Utilizing this characteristic phenomenon, we pre-activated the Ni3Al foils and subsequently examined the catalytic properties under steam addition to methanol (steam-to-carbon ratio (S/C) = 0-1.0). The pre-activated foils exhibited high catalytic activity for methanol decomposition from the beginning of the reaction under steam addition and sustained the activity during the entire reaction time. Surface analyses revealed that the Ni particles formed by the pre-activation treatment survived after the reaction at all S/Cs, attributing to the high catalytic activity.