This study examines the post-national trends of the $21^{st}$ century fashion that has embraced multiculturalism. This study conducted a literature view to explore the concept of multiculturalism and the background of post-national phenomena appearing in contemporary fashion. In addition, as a case study, the author used local and foreign fashion magazines and collections published between 2000 and 2009, in addition to other related materials available on the Internet. The objective was to analyze photographic materials in which post-national features are reflected. From this study, the post-national trends in $21^{st}$ century fashion that adopted multiculturalism are as follows: The first is that oriental culture is more actively embraced. In the past, the tendency of embracing the oriental culture was mainly developed with a focus on China and Japan, but recently the tendency has spread to Southeast Asian countries and national/ethnic minorities that include Mongolians and Tibetans that is present in more active ways that reflect oriental sentiment and philosophy as well as adopts simple images. Second, $21^{st}$ century fashion based on multiculturalism broadens the interest in the understanding of nations in the regions of Africa, Middle East, and South America and uses regional folk costumes or indigenous characteristics to create new things instead of staying within a fixed paradigm. Third, as horizontal transfer is involved in ways of looking at culture, $21^{st}$ century fashion shows a post-national tendency to use regional cultures and folk costumes of the occidental world that includes North and West Europe in addition to non-mainstream regions (as considered so far). Fourth, dress elements of many heterogeneous national cultures are combined to create multinational images difficult to define in terms of a specific national culture or clothing style.