This book presents impacts of Oromo national question on inter-state relations in the Horn. Ever since its emergence (1960s) and transformation into national self-determination (1970s) onwards, this issue has not yet been given proper attention and hence remained unabated. Instead, it has been going on, growing much deeper, wider and stronger. This has amounted to the political crisis transcending the country and affecting the relations it has with immediate neighbors. Therefore, the objective of the study is to examine the implications it has for such relations in the region. To this end, analysis of descriptive methodology relied on secondary sources is used, whose results seem to suggest that the failure to solve the Oromo national question has had negative impact on Ethiopian relations in the region and worsening regional peace and stability. This calls for paying proper attention to and amicably addressing the problem in the country and consequently it could have cooperative relations in the region. To do so, it is advisable for Ethiopia to have meaningful democracy that could provide the Oromo people with good opportunity to decide their future fate by themselves.