Learning about one's own cultures as well as other cultures is a central aspect of the cognitive dimension of intercultural understanding, focusing the individual on cultural group affiliations, belonging and questions of 'who one is'. Using a social identity lens, with a particular focus on self-categorisation theory to explore how individuals view themselves in relation to the groups to which they belong, this article presents the implications of applying self-categorisation theory to aspects of the field of intercultural understanding. From within the self-categorisation framework, the article also reports on findings from a qualitative study involving semi-structured interviews which investigated the beliefs of experienced secondary teachers working in international schools regarding the relationship between the development of intercultural understanding and identity. Teachers indicated increased awareness of primarily national group affiliation, limited engagement with the concept of multiple cultural identities, a process of distancing and creating new group affiliations, as well as some psychological discomfort and conflict avoidance.