Slavko Mihalić is one of the most famous Croatian existentalist poets. This paper mainly deals with analysis of Mihalić's poems, mostly from his first collections of poems from 1950s (Komorna muzika, Put u nepostojanje and Darežljivo progonstvo), some from his collections from 1960s (Godišnja doba and Ljubav za stvarnu zemlju) and from a collection Vrt crnih jabuka, from 1972. Before the analysis and a chapter about Slavko Mihalić, some of the most important features of philosophy of existentialism are introduced. This philosophy had a big impact on forming existentialism in the middle of 20th century. In the paper are then presented some of the most famous existentialist philosophers and writers and their impact on Croatian existentialists. Their impact on Slavko Mihalić's poetry is not affirmed, but his poetry, especially his first collections of poems from 1950s, contain themes that french existentialist writers and philosophers (Jean-Paul Sartre and Albert Camus) used in their literary works. Main literature that was used in this paper is Uvod u filozofije egzistencije by Jean Beaufret, Filozofija egzistencije by Karl Jaspers, Neizrecivo kod Jaspersa i Wittgensteina by Ante Periša, Egzistencijalistički roman u hrvatskoj književnosti by Ana Dalmatin and Izabrane pjesme by Slavko Mihalić. The analysis also relies, amongst others, on scientific works of Ante Kusić and Drago Šimundža and literary criticism of Vesna Krmpotić and Vlatko Pavletić.