The existing research of Tan Kah Kee’s museum practices focus mainly on how he developed museums as an educational institute to modernize China. This paper re-examines his contributions to China’s museum development from a longitudinal perspective and by adopting a transnational view. By contextualizing Tan’s museum exercises in his life experience as a Chinese migrant in British Malaya and through analysing the architecture design, collection and audiences of his museums, it conceptualizes the museums built by Tan as “diaspora museum”, defined as a heritage-making space constructed through the interactions between Chinese diasporas and the Chinese homeland, produced by and producing a de-territorialized vision of nation and identity. In addition, based on this case study it argues that Overseas Chinese opened up an alternative route of transmitting museology to China. Instead of transferring museum directly from Western countries, they acquired the knowledge of museum through encounters with mediated Western modernity in colonial Southeast Asia and then transmitted it (indirectly) to China. Tan’s museum endeavors laid the foundation of a “diasporic heritage-building” tradition that has had a long-lasting impact on museum development in China today and among the Overseas Chinese communities.