The article provides substantiation for the process of socialization of orphans in an orphanage. The essence of the concept of "socialization in an orphanage" is clarified. Authors consider socialization in an orphanage as the process of development of social competence of its residents that serves as a basis for orphans' relationship with society through the implementation of an individual strategy of social learning, self-knowledge, and personal self-realization that provides orphanage residents with social knowledge, socially-oriented motives, and social experience. The main block of the experimental work was carried out based on the Pavlodar orphanage in 2020-2021. The criteria and diagnostic methods for the evaluation of social competence development in orphanage residents are identified. A Model for the development of social competence in adolescents in an orphanage including the program and purpose, activity, and reflexive and predictive components is developed and implemented into the pedagogical practice of an orphanage; based on the Model for the development of social competence in adolescents in an orphanage, the "Socialization in an orphanage" program aimed at the socialization of orphanage residents is developed. The effectiveness of the developed Model for the development of social competence in adolescents in an orphanage is proven in the course of the study of specific characteristics of orphans' socialization in an orphanage. The study results are recommended for practical implementation in orphanages in the process of orphans' socialization.