Immigration is transforming the societies of Europe and North America. Yet the political implications of these changes remain unclear. In particular, we lack credible evidence on whether, and how, becoming a citizen of the country of residence prompts immigrants to engage with the political system. This paper used panel data from Germany to test theories of citizenship and immigrant politics. I found that naturalization can promote political integration, but that this is more likely if new citizens have the chance to pick up habits of political engagement during the formative years of early adulthood.