Semiotics of false friends in Russian and Croatian language. This thesis examins false friends between Russian and Croatian language, from a semiotic perspective. Paper is primarily focused on changes in the arbitrariness of the sign of the collected words. The first part of the paper presents an overview of semiotic thoughts and views on the science, as well as the most important features presented through the founders of this philosophical-linguistic discipline. The second part of the paper deals with the theory of false friends and brings a list of words to be analyzed. The words we analyze within the second part of the paper are the ones I most often encountered during the Erasmus+ program in Russia. These words concern almost all segments of human activity, that is, they are not narrowly specified in only one area. The material was approached in such a way that the etymological background of each was first determined, thus giving insight into the change in the arbitrariness of the sign. The idea behind it all was to show the emergence of the phenomenon of false friends in a semiotic framework.