Enhancing the educational experience and social connectedness for international students is the responsibility of different involved parties among whom international students themselves and host institutions play a key role. However, the question of how the condition of cross-border mobility has shaped and re-shaped international students' responsibility towards the home and host country and other social relationships that have been formed via their mobility experiences is often neglected. This paper examines the social nature of international students' responsibility. It is derived from a research project funded by the Australian Research Council that includes fieldwork and semi-structured interviews with 155 staff and international students from 25 institutions in Australia over 4 years. Using positioning theory as a conceptual framework, the study shows that it is important to take into account the tangible aspects of transnational mobility in understanding international student responsibility rather than merely locating their responsibility in simple cultural, personal or institutional parameters. The study suggests the important roles of host institutions and community in creating conducive conditions and opportunities for international students to exercise responsibility as social members and intercultural learners. Enhancing student social responsibility and capacity for enacting responsibility is essential for nurturing meaningful transnational citizenship.