Since the mid-2000s, the South Korean government has produced policies around "multiculturalism." Researchers have focused almost exclusively on what are termed "multicultural families," i.e. families where wives and mothers are female marriage migrants from other countries. Restricting the research focus in this manner presents a skewed understanding of multiculturalism and helps to legitimize the government's interest in maintaining a narrow interpretation of the multiculturalism policies. To address these limitations, this dissertation examines the inclusions and exclusions of three migrant groups - North Korean defectors, multicultural families, and migrant workers - through the lens of South Korea's multiculturalism policy. The dissertation is inspired by the Foucauldian theoretical concepts of governmentality and genealogy; it draws on anti-colonial nationalism literature to examine South Korea's particularities as a post-colonial society. The primary source of data for policy discourse analysis is textual data, centred around the National Assembly minutes (1998-2017), which is supplemented by interviews. The dissertation puts forward three arguments: First, the notion of multiculturalism was embraced to "politely" denote those cultural differences that South Korea has become willing to tolerate but at the same time to subordinate to Korean nation. Second, in the context of South Korea's political-ideological landscape shaped by the Japanese colonization and the division of the Korean peninsula, conservative forces have condemned ethnic nationalism and dominated its multiculturalism discourse while their liberal and progressive counterparts have held onto this nationalism and remained passive on migrant-related issues. Third, this dissertation shows that South Korean multiculturalism discourse has become fraught with conservative forces' preferences for certain types of migrants, i.e. migrants who are politically conservative (or passive), nostalgic for a mythical Korean-ness, and obedient to the existing economic order. Of the different migrant groups addressed in this study, it is the North Korean defectors and the multicultural families who are thought to satisfy these conservative preferences while the migrant workers do not. This study contributes analyses about multiculturalism policies in a country outside the horizon of Western studies of multiculturalism; it highlights the value of considering how South Korea's historical, geopolitical, and ideological conditions have shaped its engagement with the multiculturalism discourse.