The conflict over the Nagorno-Karabakh region between Armenia and Azerbaijan was heated up in 1991 after Nagorno- Karabakh conducted a referendum to separate from Azerbaijan’s territory and was successfully suppressed after the ceasefire agreement in 1994. However, the conflict escalated at the Battle of Mardakert in 2008 which was the biggest battle since the ceasefire in 1994. This research is carried out by using qualitative-descriptive method which aims to describe the efforts of the Organization for Security and Cooperation in Europe (OSCE) through the Minsk Group on resolving the Nagorno-Karabakh conflict year 2008-2017. Use the concept of international organization and conflict resolution through mediation. This research found that the Organization for Security and Cooperation in Europe (OSCE) mediated through field assessment missions and negotiations on resolving the Nagorno-Karabakh conflict.