This case study profiles eight international PhD students and describes the process of the construction and negotiation of their social and institutional identities in an Australian university. Audio-recorded informal conversations of the students highlight the role of social membership, staffroom interactions and language in the construction of institutional identities. The impact of multiple identity transitions experienced by new international students is described. The data analysis uses a sociocultural perspective of second language in use, which reflects the negotiation of power, space and identity in informal multicultural institutional encounters. The article provides insight into the ways transitions are experienced by international postgraduate students. Findings also include a critique of the negatively loaded stereotype of the "international student" in Australian universities and the way it underplays the heterogeneity of student experience.