In the past few decades, due to its presence in public space, street art has established itself as a very popular form of art. It can be perceived as a way of artistic expression enabling artists to introduce their work to the largest possible audience and to influence this audience by the contents of its messages. However, street art is not just one among many possible ways of expression; it is a unique form of communication that takes place in an everyday urban setting, its messages being available to everyone, at all possible times. Street art thus differs from traditional forms of art presented in museums and galleries. Adopting certain techniques from both traditional visual art and the new media, street artist experiment with these techniques in search of new ways of encoding and transmitting artistic messages. Communication through street art does not only have an aesthetic aim; it has a practical aim too – to influence the audience and to actively participate in the social dialogue. The main goal of the present thesis is to show – by reference to some distinguished street artist (both from Croatia and from abroad) – why street art should be treated as both a form of political activism and a special means of communication. In reaching this goal, the thesis appeals to the general (semiotic) theory of cultural representation as well as to the analyses of eminent street art critics.