This paper considers when and for what purposes Peer Assisted Study Session (PASS) Leaders at an English medium university use their first language (when that language is not the dominant language of instruction) to facilitate PASS sessions in an English speaking university. This small qualitative exploratory study examines the experiences of eight PASS Leaders who speak a language other than English. The paper explores how and for what purposes the PASS Leaders utilised their first language (referred to as L1) of Chinese or Vietnamese and their second language of English (referred to as L2). The research participants revealed complex and well-considered decision-making processes regarding the language(s) they used in their sessions as PASS Leaders. Broadly, the language they used depended on the linguistic backgrounds and preferences of the session attendees, the concepts covered in the sessions, and the importance PASS Leaders ascribed to learning English over learning the subject's content. We suggest that there may be room for languages other than English as a "medium of instruction" in PASS sessions. Our initial investigations warrant broader discussion and further research within the PASS/SI community about the role L1s can play in enhancing the student learning experience in PASS sessions, for both PASS Leaders and PASS attendees.