A neglected topic in empirical research on national identity is its stability at the individual level, and this is especially true for its content, that is, the meaning elements that people associate with the concept of nation. In this article, we study the stability of key dimensions of national-identity content. We ask three simple questions: How stable is national-identity content—as captured in the ethnic/civic framework—at the level of individual citizens? Are there clear differences in stability across subgroups? What are the implications of interindividual differences in stability? Analyzing data from four waves of a large-scale panel survey of German citizens (N = 4,654) collected over a five-year period (2016–21), we show that there is high but not perfect stability of the degree to which individuals subscribe to ethnic and civic criteria of nationhood. Second, we find little difference in stability as a function of several theoretically selected characteristics. Third, we show that the association between national-identity content and relevant political attitudes (immigration attitudes and far-right party support) increases with intraindividual stability. These findings have important implications for our understanding of how national-identity content is shaped and mobilized and how it can influence political attitudes and behaviors.