Despite the ostensible complementarity of the structural shortage of industrial labour in Mongolia and the excess thereof in China, Chinese workers have constituted a source of anxiety in post-socialist Mongolia. Drawing on fieldwork at a Chinese-owned fluorspar mine in Mongolia between 2018 and 2019, this essay sheds light on the tension between bilingual and monolingual Chinese workers in the Sino-Mongolian industrial sphere. While the monolinguals rely on the bilinguals to facilitate industrial production, they also regard the latter in a suspicious light.