Research on the discursive features of graffiti in institutional settings is in its infancy and few studies have investigated the phenomenon and its implications in educational contexts. In this paper, we report on a study in which we employed systemic functional linguistics (Halliday in Learning how to mean, Edward Arnold, 1975). to probe communicative functions and gender differences in Iranian university student graffiti that appeared in all-male and all-female locations. The data comprised authentic instances of graffiti generated by students, analysis of which suggests that male and female university students each have their own distinctive motives for using graffiti, as realised in significant differences observed in the context-specific functions they perform. Graffiti pieces represented a distinctive and meaningful way of communicating, and its most salient features were creativity, simplicity and variation. Indications are that university students' graffiti reflects psychological and social challenges, and the thoughts, attitudes and feelings expressed through it serve students' personal and interactional purposes.