Studies of nationhood in interwar Yugoslavia generally refrain from considering dynamic relations between different levels of collective identity available in the state. Inspired by scholarly studies which have pointed at the compatibility of national and sub-national identities, this article examines interaction between definitions of Yugoslav national ideology and Serbian collective identity in textbooks published in Belgrade. In textbooks of the 1920s the imagination of Yugoslav unity reflected the structure of Serbian national identity as it had been defined in pre-First World War Serbian textbooks, providing few possibilities for other viable sub-national definitions of Yugoslav identity. After the establishment of the Royal Dictatorship in 1929 textbooks reshaped Serbian collective identity by embedding it in a more openly defined Yugoslav whole to which different sub-national traditions could contribute. Thus, contrary to its programmatic insistence on the homogeneity of Yugoslav identity, the dictatorship's educational policy created opportunities for multiple sub-national interpretations of Yugoslav unity. (Contains 82 footnotes.)