The principal objective of this thesis is to investigate and understand the relationship between Ireland and Spain from 1939 to 1955 by researching the cultural, economic and political ties that existed between both nations. The research is based on primary sources examined in the diplomatic archives of Dublin and Madrid as well as original documents analysed through unrestricted access to private archives. The main body of files investigated centre on the reports of diplomats that reveal the nature of this relationship, which was in the main harmonious, despite the momentous internal and external challenges that confronted both countries during that period. The findings expose the perceptions held by the leading politicians towards this affiliation and why it was considered important to maintain. The results also show that ultimately the relationship proved ephemeral because it was based on antediluvian and archaic values that were incompatible with the prevailing course of history. By juxtaposing Ireland and Spain between the start of the Second World War and the admission of both nations into the United Nations in 1955, a major gap in historical research is explored that substantially assists the knowledge of this bilateral relationship. Furthermore, the research lifts a veil on the socio-economic and socio-political environments of both countries in a way that contributes to the historiographical appraisal of the period.