This paper aims to explore the main causes of the characteristics of North Korean (NK) English textbooks that have been accumulated from previous studies. To this end, Socialistic Educational Theses and 32,897 words of NK top leaders’s talks were digitized for analysis, and NVivo 13 was used to thematize the data. The findings are as follows: The different lesson structures of NK English textbooks are caused by Kim Il Sung, Kim Jong Il, and Kim Jong Un, despite their common footings on Socialistic Educational Theses. Despite the differences in the lesson structures, there is a consistency in the emphasis of social ideology, criticism of capitalistic society, combination of theory and labors, importance of physical diligence, and importance of science and technology as topics included in the NK English textbooks. The foundations of such an emphasis as topics in NK textbooks derived mostly from the words of the NK top leaders. In other words, the characteristics of NK English textbooks are largely influenced by the political ideology of the Kim family. The textbooks are designed to indoctrinate students with the Juche ideology and to prepare them for a life of service to the state.