Contrary to popular belief, South Korea is not immune from the growth of Islamic radicalism. Although no serious terrorist attack has yet occurred within the country, some worrisome incidents have been reported. Recently, an Indonesian man was arrested on the grounds that he publicly supported the Al Nusra Front, a known Al Qaeda–affiliated terrorist organization, and even attempted to depart for Syria to join the organization. The current study is a response to such an incident. It investigates whether such an incident is an isolated exception or a harbinger of the Islamic radicalization process within South Korea, particularly within the Muslim immigrant community. The current study focuses primarily on the Indonesian immigrant community within South Korea but also investigates other Muslim communities when needed, as Muslim immigrant communities are often intermingled and share similar features. The study found some worrisome developments of Islamic radicalization within the Indonesian immigrant community in particular and the Muslim immigrant community in general. Using the enculturation stress model, the current study explains that such Islamic radicalization is a pathway of the collective response to cultural adaptation stress that most Indonesian and other Muslim immigrants face within South Korea. To conduct the study, ethnographic qualitative interviews were used. Indonesian immigrants, their Korean spouses, civilian activists, civilian aid workers, government officials, police officers, immigrant agency officials, and security officials were contacted and interviewed. Each interview lasted between approximately one and four hours. The limitations of the study are also discussed.