Despite an increasing number of children from culturally and linguistically diverse backgrounds living in South Korea, their languages have not received sufficient attention in Korean schools and society. This article aims to identify the language ideologies operating in Korea by examining the ways languages are situated in multicultural research and practices. To present the background of the study, the author reviews the demographic complexity of the culturally and linguistically diverse (CLD) populations in terms of language and ethnicity. Then, by examining multicultural research and policies regarding use and education of diverse languages in Korea, the author argues that three interrelated language ideologies (language stratification, double standards in multilingual education, and deficit and remedial paradigms towards multilinguals) underlie Korean multicultural education, supporting monolingualism rather than multilingualism. The article highlights the discrimination and inequity that minoritized students encounter when their languages are not considered cultural capital or a valued part of their identities. Then, the author offers the following suggestions for redesigning multicultural education in Korea: providing institutional support for multilingual teachers, integrating critical multilingualism in teacher education, and implementing translanguaging practices in language classrooms.