Linguistic aspects of transnational organized crime are wide-reaching in type and impact. These linguistic aspects need greater and sustained attention if we are to understand and respond to crimes such as human trafficking. Transnational organized crime, including human trafficking, can be seen as a modern societal crisis that presents major challenges for policing, justice, and human rights (Beare, 2003). In Translation Studies, globalization has mainly been considered in relation to our interconnected and diverse societies, and the resulting impact on interpreting and translation (e.g. Cronin, 2003; Inghilleri, 2017; Pym, 2004). The corresponding – and linked – growth of the ‘dark side’ of globalization, transnational organized crime, has not received a similar degree of attention (Heine and Thakur, 2011; Bowling, 2009). This chapter draws on original research focused on the experiences of frontline workers in cases of human trafficking in the UK and Belgium (police, border agencies, support services, the Red Cross and others, including specialist linguists) and investigates the barriers to communication which they encounter. By demonstrating the critical role of language for those working to prevent and prosecute crimes of human trafficking, the chapter addresses gaps in understanding in fields including Criminology, International Relations, and Migration Studies.