The article presents a retrospective analysis of adult learning development in Poland in the 20th century. Based on the study and analysis of historical and pedagogical literature, normative documents of the official bodies of Polish government, the periodical press of the 20th century, several stages of adult learning development, in the particular historical period, have been determined: 1905-1913 years were defined by the legalization of educational institutions for adults, the search for new forms and methods of education, the involvement of a wide range of people; 1914-1945 was the stage of world wars that had led to the destruction of the adult learning system, which led to the decline of educational institutions; 1950-1960 years were characterized by the restoration of adult learning institutions, the adaptation to the new political system, a new approach to formulating the goals and objectives of adult learning; in the 70s and 80s of the 20th century, there was the cardinal rethinking of the goals and objectives of adult learning, educational institutions practiced new forms and methods of teaching, the idea of lifelong education was widespread in the society; the period of the end of the 20th century had initiated the integration of adult learning in Poland into the Common Educational Space, which contributed to the intensification of the theoretical substantiation and practical implementation of the international concepts of adult learning. Among the criteria for determining the stages, there were socio-political, socio-economic, organizational and pedagogical factors that led to the change of subjects, goals, objectives, content, principles, forms, methods of organizing adult learning in Poland in the 20th century. The historical and pedagogical features of each stage are shown, the influence of historical events on the formation and development of adult education in Poland is taken into account and analyzed. In accordance with each stage, the leading forms and methods of adult learning are have been determined. The peculiarities of the activity of adult learning institutions at all stages have been demonstrated. The disadvantages of the adult learning system, as well as the difficulties of its development, have been identified.