The purpose of this paper is to evaluate the role of Nigeria as a Hegemon in maintaining peace and stability in the West African Sub-Region and its current reversal while confronting the Boko Haram (BH) insurgents. Due to the scarcity of basic essentials of live such as food, health, education, and shelter in the West African Sub-Region, comes the inadequacies that led to the growth of impoverished, uneducated, unemployed, hunger-stricken and restive populations all over the Sub-Region. The effect of the above scenario is the prevalence of conflict between ethnic nationalities leading to instability in some countries of the region and threat to their National Security. Nigeria, as one of the sixteen states of the sub-region was worried about the rising conflict in the region due to its effect on the people in the areas of peace and stability. So, as a hegemon in the region due to its strong economic and human resources as well as its military power through the formation of Economic Community of West Africa (ECOWAS), it was able to assist in many ways to bring about peace and stability in the region. But very unfortunate for Nigeria, the reverse has become the case as it has been confronted with the menace of Boko Haram insurgency with its aim of compelling Nigeria to fully implement the Sharia system of governance and consequently Posen serious threat to its national security with activities which include killing, abduction and destruction of both private and public properties with the Nigerian military that assisted other West African countries in peacekeeping been unable to contain the deadly insurgent group and instead seeking for assistance from the neighboring countries in its fight against BH. The objective of this paper is to evaluate the role played by Nigeria in peacekeeping in the West African Sub-Region and why the reversal for the country despite its strong army that assisted other West African countries. The method adopted was that of qualitative where documentary data such as journal, texts and news papers were evaluated and analyzed. The finding shows that while Nigeria was able to use its military and economic might to assist in bringing peace and stability to some conflict riding counties in the region, it has been unable with the same military to combat the Boko Haram insurgency, instead, it is now seeking for the assistance of the neighboring countries and Western countries to come to its assistance in combating the Boko Haram.