The present article intends to examine how ethnic minority group members account for their ethnic identity as part of a series of interviews with young Mapuches on what it means to be Mapuche in contemporary Chilean society. The focus is on the actual accomplishment and display of ethnic self-definition and group identification. We draw on insights from discursive psychology to explore some features of common-sense practical reasoning that ethnic minority group members use to negotiate, self-ascribe or resist a particular sense of identity, and to produce observable and reportable identities. We have a particular interest in illustrating how ethnic self-definition can be seen as the contingent outcome of a practical and interpretive issue for members of society, with a special focus on how ethnic minority identity is constructed through the flexible use of group-defining attributes and characteristics, categories and common-sense categorial knowledge. We suggest that understanding the complex significance and meaning of ethnic self-definition for minority group members is dependent on engaging closely with its occasioned context of production and treating social identities as a feature of how people describe themselves. It is argued that this view of ethnic minority self-definition as a practical and interpretive issue and as a discursive product in action can provide a further contribution to literature of both discursive and intercultural studies of ethnic identification of minority groups, intercultural and interethnic relations.