This paper examines emblematic texts by two important protagonists of post‐1848 liberalism in Germany, Gustav Freytag and Heinrich von Treitschke, focusing on their treatment of Jews and Poles. The paper analyses the social content of their statements and argues that the elements of anti‐Semitism and anti‐Slav racism that they contain were motivated by the specific kind of nationalist liberalism that frames their affirmation of the process of modernisation. This affirmation was directed against the Poles on the one hand, seen as backward Easterners who had to be pushed into civilisation by Prussian–German colonialism, and, on the other hand, the Jews, largely perceived as representing the wrong kind of modernity against which benign (supposedly German) modernity had to be protected. At the same time, the image of the Jew in Freytag and Treitschke also participates in that of the backward Easterner, permitting to see undesirable, allegedly Jewish aspects of modernity also as distortions resulting from an alien and ancient culture. This analysis has consequences for theorisations of both liberalism and nationalism: it suggests that the racism and anti‐Semitism of nationalist liberals were intrinsically related to core aspects of the liberal world‐view rather than being merely contingent opinions held by particular individuals. It also indicates that the nationalism of many German post‐1848 liberals was ethnic as well as liberal. In this way, the paper contributes to the growing body of literature discussing the illiberal aspects of liberalism as well as the shortcomings of the long‐established conceptual dichotomy of ethnic vs. liberal nationalism.