This study researches the historical development of the self-understanding of the Old Catholic Churches of the Union of Utrecht and the Iglesia Filipina Independiente. Throughout the 20th century, both churches have been in a developing relationship with each other, resulting in full communion in 1965. In the same time period, both churches developed an ecclesiological self-understanding in which an ecclesiology of the national church gradually gave way to an ecclesiology of the local church. By outlining this development for each of these two churches and comparing the developments, the study gives insight both into the individual development of the two churches involved and shows how these developments relate to each other. In this way, the study presents a new historical portrait of these churches and their self-understanding.