South Korea has emerged as a major destination for labor migration in the Asia-Pacific region in the last two decades. In 1991, the total number of foreign-born population in Korea was 167,000. At the end of 2011, the number reached 1.4 million while 705,000 of them are estimated to participate in the Korean labor market. The migration process has largely been government-driven and shaped by two policy goals. First, unskilled migrants were allowed in to mitigate the labor shortage in the small and medium enter-prises but only on a temporary and limited basis. Second, skilled migrants were actively sought and allowed to migrate to Korea under favorable conditions. Yet twenty years later, the results are rather disappointing. Contrary to the policy intentions, the majority of migrant workers in Korea are unskilled workers, whereas skilled workers account for a tiny fraction of the foreign labor force (6.8%). The arrival of unskilled workers has certainly reduced chronic labor shortages in certain sectors of the Korean economy, such as manufacturing, agriculture and livestock farming, and construction. It has, however, raised a host of serious social and economic challenges. The immediate concerns are the potentially negative impact of migration on the employment and wages of Korean workers. A large population of undocumented migrants, a much higher share than Taiwan and Japan, continue to be a problem. It has also been suggested that the continuous supply of cheap labor keeps in place industries that would not have survived otherwise. Finally, the arrival of migrants, often with lower socioeconomic status, has created social and cultural tensions in a country unfamiliar with ethnic and cultural diversity. On the other hand, government efforts to recruit highly skilled professionals from abroad have not been very successful. The challenges associated with labor migration in Korea require a comprehensive overhaul of Korea’s foreign labor policy. Yet, understanding the “supply side” — the structural and policy factors that contribute to labor migration in origin countries — will help improve bilateral labor cooperation. Aside from China, Southeast Asia is the largest sending region of migrants to Korea. Of the foreign population in Korea, 20% are from Southeast Asia. Understanding the structural and policy factors behind the migration of labor from Southeast Asia can therefore help better understand migration issues between Southeast Asia and Korea. This brief examines the structural factors and government policies that drive labor migration from four Southeast Asian countries: Vietnam, Indonesia, the Philippines, and Thailand.