This paper deals with the reconstruction of the mythological background of the most important folk customs in Croatia. These customs are listed in calendar order, starting from Christmas, through Carnival and St. George's processions, all the way to St. John's feast. Perun and Veles are presented as key factors in the mythology of the ancient Slavs and Croats, since their motives, as the motives of the supreme gods, are the starting point for finding mythical elements in oral literature. When it comes to the customs themselves, an analysis begins with the presentation of Christmas carols, in which the beginning of the mythical cycle about natural changes is hidden. Then we move on to the carnivals which is by calendar sequence after Christmas, but when it comes to the myth that lies behind this custom, they belong to the very end of the this paper. Then we move on to the feast of St. George and St. John. By accepting Christianity, almost all motifs of the old religion are layered with Christian ones, but some of them can still be found in oral traditions and poems that most authors used as a starting point of their research, and have been used for this purpose in this paper as well. The purpose of this paper is to show that most of the Croatian folk songs, those songs that have a mythical theme that is, were once pagan ritual songs, as well as that the folk customs associated with these songs were once pagan rituals.