Studies have widely documented the strong opposition to nuclear weapons among the Japanese population. Yet, present research questions the robustness of the anti‐nuclear norms in Japan. Since Japan has been largely dependent on the United States for its security, shifts in the U.S. nuclear strategy in East Asia will significantly influence public attitudes toward nuclear armament in Japan. By taking advantage of the situation in which Donald Trump suggested the withdrawal of U.S. troops from Japan, this study examines the relationship between Japanese citizens’ faith in the U.S. “nuclear umbrella” and their commitment to the anti‐nuclear stance. Results of the statistical analyses show that declining faith in the U.S. nuclear umbrella significantly boosts Japanese citizens’ support for nuclear armament in their country, thus generating critical implications that are highly relevant in understanding the security culture in Japan.