AbstractWhen people feel uncertain about their national identity, they may want to emigrate from their nation. This uncertainty can arise when people are exposed to an alternative historical narrative about their own national (ingroup) origins promoted by a neighboring nation (outgroup). Drawing on uncertainty–identity theory we propose that the conditions that promote this process would include when: (a) a revised history threatens the entitativity of national identity, (b) people identify strongly with their nation, (c) a neighboring nation is numerically large enough to transform its own view into a new shared reality, and (d) a new interpretation of history is considered credible. We conducted an experiment in the context of historical disputes between China (outgroup) and Korea (ingroup) (N = 160). We measured Korean identification and manipulated a type of identity threat (valence threat vs. entitativity threat), relative group size (not salient vs. salient), and source credibility (low vs. high). Then, we measured identity–uncertainty and emigration as dependent variables. As predicted, hierarchical regression analyses yielded a significant four‐way interaction on identity–uncertainty. Simple slopes analyses revealed that entitativity (vs. valence) threat significantly increased identity–uncertainty among high identifiers when the outgroup's relative size was salient and its view was credible. Further, the elevated identity–uncertainty strengthened intentions to emigrate from the ingroup. Implications for intergroup communications and identity validation are discussed.