From 1950 to 1964, in response to a request from the Mongolian government, the Chinese government sent more than 20,000 workers to Mongolia in order to assist in its socialist construction. Making use of Chinese, Mongolian, and Soviet official documents, this article reconstructs the origins and process of sending Chinese workers to Mongolia. It shows that when the Chinese Communist Party and the Mongolian People’s Revolutionary Party were friendly with each other, China and Mongolia could tolerate disagreements and their respective failures to honor their agreements on the treatment of Chinese workers in Mongolia. However, when relations between the two partners soured, these workers became the scapegoats by which each side criticized and defamed the other. From the Chinese workers’ perspective, although they were passively involved in the personnel exchanges between China and Mongolia, they did become the crux of Sino–Mongolian relations under special circumstances. At the same time, affected by the fluctuations in those relations, some of them were imprisoned and some even paid the ultimate price with their lives. The fates of “ordinary people” who were involved in interactions between socialist countries in the context of the Cold War deserves attention and further study.