Modern society requires teachers’ training as a three-part task, which includes the education of professional motivation and determination; ensuring legal competence; development of teachers’ professionally significant personal characteristics. The peculiarities of the objects of future primary school teachers’ professional activity require rethinking of the content and methods of their teaching, forming their legal competence. The aim of the article is a theoretical substantiation of the conceptual fundamental of legal competence formation of future primary school teachers. In the article, we applied such research methods as analysis of literature and information sources on the research problem, the generalization of theoretical provisions, and teachers’ pedagogical experience. The principal tasks of legal competence formation of future primary school teachers include the coordination of the purpose of legal education and professional training, logical sequence of legal knowledge and skills development, substantiation of the legal component in primary school teachers’ professional training, substantiation of the provisions of the legal aspect in primary school teachers’ training, ensuring the continuity of legal training of students, target models development of the legal aspect in primary school teachers’ training, the development of complex educational and methodical support of legal education, organizational support of the legal aspect in primary school teachers’ professional training using the appropriate training of the teaching staff of establishments of higher education, providing motivation for learning legal disciplines, and computer support of legal education of primary school teachers. The legal competence formation of future primary school teachers is to be considered as the pedagogical system created due to scientifically proved approaches, theoretical and practical achievements of Ukrainian and foreign pedagogy of higher school, the concept of continuing education, considering major tasks of the formation of Ukrainian integration. During legal competence formation, a close relationship between professional and legal, humanitarian, and technological components of the educational process is to be established. The theoretical substantiation of legal competence formation is based on the philosophy of education, personality-oriented learning, opportunities, and needs of the industry and objects of their professional activity.