This paper analyses functions and semantics of borders in the Slovak and Czech fairy tales. The study attempts to verify a hypothesis about the cosmological value of borders and boundaries like water surfaces, bridges, houses or woods in fairy tales, which are connected with the Indo-European and Slavic mythology based on G. Dumézil's theory. These borders include also magical value, because they delimitate the outside world and so they create two opposite, but perpetually connected faces of the world – inside the borders there are guaranteed stability, safety, health, life and peace for all characters and heroes of fairy tales, but outside the borders rule instability, fear, death and chaos. The hero crosses over the border to an unknown place, because he is displeased at the circumstances and wants to change his position in the society or find a princess that is when the process of his initialisation begins. The element of crossing over the border seems to be a magical ritual of pilgrimage to another world, in which the hero has been attacked by dark power (witches or forest robbers). The hero takes something from them and then he escapes back to his world coming through the borders, which cannot be violated by a dark power. His success lets him constitute new order and demark his world with new rules (cosmological and magical act).