After the First World War, the province of Transylvania ceased to be part of a multinational empire and became part of a national state. Before 1918, in the context of the Austro-Hungarian Empire, Transylvanian Romanians represented a minority and were under Hungarian rule given that Hungarians formed the majority at the time. When the province joined the Old Kingdom of Romania and became part of the newly-created national unitary state, the status of Transylvanian Romanians changed. From then on, they formed the majority. The first part of the present study examines the change of status from ethnic minority to majority and the relationship between the Romanian and Hungarian communities in the context of the newly-created Romanian national state during the interwar period with special focus on the province of Transylvania. It also investigates the identity aspects (language, religion and history) which confer specificity to the Hungarian minority, the self-perception of Hungarians within the national state, as well as the manner in which minorities represented themselves in a Romanian state that aspired to be nationally, spiritually and linguistically homogenous. The second part of the present study assesses the legal provisions pertaining to the status and protection of ethnic minorities in international treaties as well as the Romanian legislation. Special emphasis is laid on the provisions of the Treaty of Versailles and the Treaty of Trianon on the one hand, and the 1918 Union Resolution of Alba Iulia and the 1923 Constitution on the other as the most important legislation of that time. The conclusions analyze the meanings that the reconfiguration of identity carried for the Hungarian minority in Romania. The analyzed data was collected from political literature, newspapers, as well as published reports and legislation. This research represents a case-study that provides a new perspective on the historical relationship between ethnic majorities and minorities, more precisely between Romanians and Hungarians in interwar Romania.