The article deals with the concept of I. Franko on the development and functioning of the Ukrainian language and its dialects. On the basis of works of the author’s works "Literary language and dialects" and "Speak of the wolf – say for the wolf", modern views on the problem of national and literary language have been formed. The historical-stylistic approach allows to comprehensively analyze Franko’s views on key linguistic concepts – literary language and literary norm as well as a tangent to it – dialectal speech, linguistic flair, the culture of speech, etc. The role of I. Franko in the language disputes at the end of the 19th century is being outlined, in particular his work assesses and determines the role of the figure in the views of contemporary linguistic problems, the place of dialects in the language system, the dynamics of language processes at the end of 19th and beginning of 20th centuries, new trends in the development of lexical and phraseological fund of the Ukrainian language, the enrichment of the stylistic resource of the Ukrainian language, the role of socio-political processes on the state and quality of the Ukrainian language, etc. The author makes a digression to the life and work of I. Franko, specifically to scientific contacts with V. Jagić, J. Collares, M. Grushevsky which allowed to trace the interdependence in the problems of the formation and functioning of the literary language in Serbia and Croatia, Bosnia and Herzegovina, Montenegro, Slovenia, and Macedonia. Consideration of the "single Ukrainian language" for Franko is a key issue addressed in the works of both scientific and journalistic nature. It is important that both Franko and his contemporaries-Slavists, saw in the unity of the language a mental-national character of Ukrainians, which is confirmed by the epistolary heritage of the scientist and can be promising for further analysis of current problems of the Ukrainian language past and present.