In 1972, representatives of the Northern Sudan and the Southern Sudan reached a historic agreement to end the first bloody civil war in Sudan by way of negotiations, in which the third party mediator (Ethiopia) had participated in the peace process. However, the Addis Ababa Peace Agreement had faced serious challenges for its implementation and as a result in 1983 it failed to bring sustainable peace between the two peoples. This thesis attempts to answer the research question: why the Addis Ababa Peace Agreement did fail? It thoroughly goes through the dominant conflict resolution theories and it uses a contemporary theory based on power-sharing and negotiation theory. The thesis will partly highlight the root causes of the war as the main cause for the beginning of the first civil war in Sudan. The thesis concludes with the final failure of the Addis Ababa Peace Agreement by stating all the important factors: the social, economic, security and political dimensions.