This paper describes the classification of the functions of preverbs in Georgian and the other Kartvelian languages as a contribution to the typology of this issue. Preverbs have different meanings and activities in different languages. The typological classification of the functions of preverbs reveals the four core functions: spatial, temporal, objective and lexical. This paper discusses verbal argument structure alternations encoded by preverbs. I argue that preverbs affect verbal valency changes and stimulate object role-shifting in Georgian verbs and other Kartvelian languages. I also argue that preverbs have a crucial role in object alternation across the languages.