This article investigates codeswitching, codemixing, and other bilingual speech phenomena in interpreter-mediated  interaction, a type of data that has been largely ignored by linguists working on bilingualism. It is argued that important theoretical considerations exist for considering such data, as it represents interaction between speakers of the different languages that are in contact (exolingual interaction) and thus enables the researcher to link micro-sociolinguistic observations about the interaction to macro-sociolinguistic facts of the contact situation more generally. Investigating data from arbitration hearings in New York City courts during which speakers of Haitian Creole, Polish, Russian, or Spanish interact with English speakers, it is shown that bilingual speech phenomena like codeswitching to English and insertion of English lexical items in other language structures pattern in ways that parallel the findings of more traditional studies that draw on in-group interaction. However, it is argued that their asymmetrical distribution can be directly related to the power asymmetries that hold between English-speaking court officials and other-language-speaking court users. Furthermore, it is shown that investigating interpreter-mediated  interaction has several methodological advantages, as it facilitates a cross-linguistic comparison across parallel interactional episodes and avoids several problems of researcher access and observer effects that often constrain codeswitching studies.