The history of identity in early 20th century Palestine has often been depicted in terms of struggles between divergent and newly-formed nationalisms determined by the delineation of pseudo-national mandate borders. Rarely does this history refer to the post-war Treaty of Lausanne’s provisions nationality related to state succession in the Arab provinces of the former Ottoman Empire. Standard histories of the Palestine mandate also often exclude a nuanced analysis of how the inhabitants of the mandated territory experienced the transitions in legal status from Ottoman nationals to Palestinian citizens. The mandate borders recognized in the post-First World War period did not translate into any sudden cast-off of Ottoman nationality and citizenship notions. The current paper, based on Palestinian Arab and British colonial primary sources, uses the historical creation of borders in the interwar Levant as the framework to juxtapose the creation and imposition of Palestinian citizenship before and after 1925 by the Palestinian Administration’s British colonial officials with the continued existence of a strong identification by the territory’s natives as Ottoman-Arab nationals. The paper traces how the restriction of certain identities and promotion of other identities played out in interwar Palestine in light of restrictions imposed through new boundaries. These boundaries of citizenship were both political (eg, borders and documentary identity) and ideological (eg the development of differences between Palestinian Arab citizens and Palestinian Jewish citizens). The paper argues that the Palestinian Arabs created their own notions of citizenship in the early mandate period in reaction to and based on the effects of the imposition of a legal citizenship and nationality status due to post-war international treaties and British legislation. It offers insight into what the new statuses meant for the ways in which the Arabs chose to negotiate citizenship vis-à-vis their former Ottoman nationality and the new Jewish Palestinian citizenship. The paper shows that citizenship itself became a border for the Palestinian Arabs once the British ratified legislation to regulate that status: mandate citizenship effectively denied the existence of an Arab nationality. Finally, the paper demonstrates how these boundaries between Arab and Jewish colonial citizens, caused by the institutionalization and bureaucratization of mandate citizenship, were negotiated, reinforced and superseded by the citizens themselves.