The Croat national issue was in the focus of many works of Miroslav Krleža. Many of the then young people, like the first president of the independent Republic of Croatia Franjo Tuđman, shifted from supporting the Croat Peasant Party to supporting the Communist movement influenced by Krleža's insights in the national question. This thesis shows the development of Krleža's opinions on the national question through the analysis of his political essays and books of talks with Krleža. The purpose of this thesis is establishing the reasons why Krleža's insights in the national question influenced the inclusion of many people in the Communist movement. It was established that Krleža was early to accept the Marxist-Leninist principle of self-determination as a desirable model of liberating non-Serb nations inside the Yugoslav frame. This thesis shows that Krleža accepted Marxist-Leninist views early on and remained faithful to them until his death, although he started doubting that socialist Yugoslavia could be preserved after the death of Josip Broz Tito. It is possible to conclude that Krleža's insights in the national question drew many people in the Communist movement because he had clearly shown the connection between the national and class question. It was especially important that Krleža had not been proving the connection through evoking of abstract Marxist phrases, but through examples from national history from which he had concluded that , throughout Croatian history, the upper classes had always been pacting with foreign forces out of fear of popular masses while simultaneously indoctrinating those same masses with national myths. Therefore, Krleža thought that the national liberation of Croats could only happen simultaneously with the class liberation of suppresed popular masses inside Croatia.