This paper explores the dynamic construction of expert and novice identities in language-exchange conversations between Korean students learning English and American students learning Korean. Drawing on recent view on identity as performance (Butler, 1990), this study employs video- and audio-recordings of language-exchange interactions to examine the dialogic interaction between three language-exchange pairs. Adopting a conversation analytic perspective, the study examines whether and how participants of language-exchange interactions orient to their assumed roles as peer-teacher and peer-learner during language-exchange through micro-analysis of the interaction. The findings demonstrate that participant roles as linguistic expert and novice are not invoked in language-exchange interactions unless they arc treated as relevant in the interaction; rather than foregrounded by the situational arrangements of language-exchange, the expert-novice relationship in language-exchange dialogues is interactionally constituted by the local practices of the participants. Data analysis also shows that the construction of expert and novice identities in language-exchange interaction is a jointly constructed achievement and that participant roles as language expert and novice arc not given but ‘achieved’ as language-exchange participants ratify or reject the identity their partners display in the course of unfolding interaction.