Caodaism was established in the South in 1926. It has been considered as one of indigenous religions in Vietnam in the first half of 20th century. In the first days, trend of Caodaism was to develop in foreign countries through missionary campaigns. Cao Dai’s dignitaries carried out missionary task in Cambodia, France, German, China… That was why followers of Cao Dai (Cao Dai followers) lived in these countries in the early 1930s. After 1975 many people in the South emigrated to America, Australia. Many of them were Cao Dai followers. After their lives have been stabilized, they have gathered to build temples so Caodaism in foreign countries has developed strongly. The number of believers in foreign countries is about 50,000 believers. They have created connection with Cao Dai sects through many forms. In this article we mention three main contents: 1) Cao Dai followers in foreign countries: the process of establishment and development after 1975; 2) The administrative relation between Cao Dai followers in foreign countries and Cao Dai church in Vietnam; 3) Some remarks on the administrative relation. The information in this article has been completed with two research methods: in-depth interview and participate observation.