Using data from a multisited ethnography of Ecuadorian transnational musicians, I applied Lave and Wenger's (1991) concept of legitimate peripheral participation and Jacoby and Ochs's (1995) notion of co-construction to examine two musicians' attempts to learn Quichua, an Ecuadorian indigenous language. Through an analysis aided by constructivist grounded theory (Charmaz, 2006), I found that co-constructed notions of language beliefs, ethnic identity, and community perspectives led to perceptions of these individuals as legitimate or nonlegitimate learners of Quichua. These co-constructions played a role in a successful acquisition of Quichua for one individual, for whom Quichua was a heritage language, and a failure to succeed by the other. The results of this article enrich discussions on maintenance of threatened languages and add to the ongoing debate in second language acquisition on the importance of cognitive/individual versus social/external factors in language learning.