Through the application of the Douglas Fir Group's transdisciplinary framework, this study investigated how three levels of mutually dependent influence (i.e., the micro level of social action and interaction, meso level of sociocultural institutions and communities, and macro level of ideological structures) operate across time and space to shape a bilingual heritage language learner's study-abroad (SA) experiences. Data were collected from standardized proficiency tests; language contact profiles; pre- and midprogram surveys; and interviews with the learner, classroom instructors, tutor-roommates, host family members, and the director of the SA program. The transdisciplinary framework enabled this study to expand its research focus and analytical scope, demonstrating that language learning was mediated by the three levels of mutually dependent influence in a dynamic and complex manner. This study has generated a richer understanding of multilayered complexity in heritage language development, advanced bilingual performance and proficiency, and bilingualism in language education and society.