Language exchange refers to a learning partnership between two learners with different native languages who collaborate to help each other improve their proficiency in the other's language. The purpose of this study is to examine the ways in which language-exchange participants activate learner agency to construct opportunities for learning in face-to-face language-exchange interactions. Adopting "affordance" [van Lier, L. 2000. "From input to affordance: Social-interactive learning from an ecological perspective." In J. P. Lantolf (Ed.), "Sociocultural theory and second language learning" (pp. 245-260). Oxford: Oxford University Press.] as a conceptual framework, this study investigates learner agency manifested in language-exchange interactions by focusing on participants' use of affordances in initiating talk about the target language and/or culture. Participant interviews are used to examine learners' perceptions of language-exchange learning and the affordances it offers. The results show substantive variation between participants in the ways they mediate affordances in language-exchange interactions. Their choices and actions in the interaction are affected by their perceptions of language-exchange learning and their mutual relationships with their partners. The study suggests that learners may develop an increased sense of agency through language-exchange interactions. It also reveals that engagement in metalinguistic and intercultural dialogues is not an automatic product of language-exchange interactions but is a demonstration of the learner's conscious efforts to create opportunities for learning.