The article is devoted to the activities of Sunday schools, which played an important role in teaching adults in the late 19th and early 20th centuries. These schools appeared during the period of socio-economic transformations, when the tasks of the school policy of tsarism led to changes in the education system. In the 60s and 90s of the XIX century, under the influence of the social and pedagogical movement, schools had to meet the socio-economic needs of the country. During this period functioning of educational institutions, in particular Russian schools, the expansion of the school network and an increase in the number of students, the creation of periodicals, the opening of libraries - all these served as a powerful impetus for the spiritual renewal of the Azerbaijani people. Of course, with the development of the oil industry, shipping and trade in the late 19th and early 20th centuries, Baku suddenly became a large industrial city. In addition, cotton, and silk productions and agriculture, were improved here. As a result of such social development, an urgent need arose for educated and talented people who knew the Russian language and were able how to use modern technologies. Starting from the last years of the 19th century, educational institutions serving this purpose began to appear. During this period, Sunday schools were one of the types of educational institutions teaching the illiterate population. These schools were called "Sunday" schools because they were open only on Sundays. The article shows the history of these schools: describes the organization of the teaching and learning process, provides information about the teaching staff, the school's working hours, providing students with textbooks, and learning aids. The role of these schools was emphasized since the graduates of these schools had the opportunity in the future to study in various vocational schools and contribute to the development of the whole.