After the Evangelical-dominated Territory of Memel (the Klaipėda Region) had been integrated into the Republic of Lithuania in 1923, the issue of the situation of the Catholics, non-dominant religious group in the region, accounting for 5 per cent of its population in 1925, had to be solved. In 1926, they were separated from the Diocese of Warmia, and joined the newly formed Klaipėda Prelature, part of the Diocese of Telšiai. Thus, the Catholics of the Klaipėda Region were integrated into Church structures controlled from Lithuania, unlike the Evangelicals, who remained part of the composition of the Prussian Evangelical Church. This paper, mainly on the basis of ecclesiastical documents, presents for the first time a broader analysis of the structure of the Catholic Church and its activities in the Klaipėda Region, as part of Lithuania, in the years 1923 to 1939.