Karakorum, in present-day Mongolia, was the first capital of Mongol empire and has often been portrayed as the cosmopolitan city par excellence of its era. This portrayal is primarily based on the description of the city as a multicultural community in a travelogue written by the Franciscan monk William of Rubruck, who spent some time there in 1254. This understanding of cosmopolitanism stems from a colloquial sense of the term and does not take into account its history and layered meanings. Based on a discussion of the term, this article presents an approach to cosmopolitanism suitable for archaeology, namely by examining the practices of ‘lived cosmopolitanism’. Taking the archaeological evidence from Karakorum as a case study, the author explores the cultural fields of city layout and architecture, cuisine, religion, and funerary rites to answer the question of whether and how the people of Karakorum were cosmopolitan. The discussion shows that it is of the utmost importance to distinguish between social groups and their status. While the Great Khans can be viewed as cosmopolitans of their time, the commoner population of Karakorum appears rather to have been segregated into different groups. The material evidence so far points to low degrees of engagement among different groups within the city. Yet, the discussion of cosmopolitanism reveals deeper insights into the social realities of the city’s inhabitants and unresolved questions in the study of this important city.