This article is the first attempt to do a complex analysis of A.A. Fet’s libretto “Dnieper Mermaids”. Fet’s text proves to be of folklore origin when comparing and contrasting this text with those by O.M. Somov, V.A. Zhukovsky, A.S. Pushkin, M.Y. Lermontov, N.V. Gogol. The main difference of Fet’s text from his predecessors’ is the elaborate system of demonistic characters (the mermaid family, the dead fiance, water goblin, wood goblin) derived from Slavonic mythological poetic images, wide range of folklore prose material and culture.