In the current neoliberal era, work is increasingly connected to transnational relations that involve people crossing linguistic and national borders. Based on a multi-sited ethnography, this article explores a transnational social movement called Emmaus where voluntary work, geographical mobility, and language learning intersect. I analyse the role of language in narratives of mobile volunteers, or those with this intention, in the Emmaus network. Volunteers need to learn and use linguae francae (English and Spanish) for voluntary work, which they justify with inter-cultural and solidarity tropes. In addition, they must also navigate nation-state immigration laws and linguistic differences that contrast with their construction of Emmaus as a 'safe zone' for transnational mobility and communication.