This chapter discusses the role of cognitive bilingualism in translation and interpreting research. It begins by presenting some definitions of translation, interpreting, and the complex notion of bilingualism followed by a brief historical account of important research in this area. Next, several core issues that have moved translation and interpreting studies forward significantly are discussed, including language proficiency and translation direction, lexical-conceptual representation and mediation, a dynamic view of bilingual and trilingual memory, and working memory and lexical retrieval. Many of these areas of study are informed by theoretical models in bilingualism which are also presented. The chapter reviews interdisciplinary methodologies that demonstrate how techniques from cognitive science have situated themselves effectively within translation and interpreting studies. Finally, the chapter discusses how technologies affect translation and interpreting research and practice and comments on how future work in bilingualism can continue to inform translation and interpreting studies.