In October 2004, there was a conflict in Southern Thailand between the Thai Government and Muslim Pattani. The root of the conflict began when the Pattani Sultanate was made a territory of the Kingdom of Siam through the Anglo-Siam Treaty in 1902. The neglect of culture in the form of religion and language was the cause of the conflict. This Pattani conflict has attracted the response of the Islamic Cooperation Organization (OIC) to get involved in handling the Pattani Muslim issue. Analyzed using the concept of International Organizations, this study concludes that the role and function of the Organization of Islamic Cooperation (OIC) as an international organization can reduce the flow of conflict and contain the conflict so that it does not spread.