Peacekeeping operations have assumed a centre stage in the operation of International Organization as a veritable instrument for maintaining International Peace and security. The United Nations and other regional and sub-regional organizations have adopted these measures in their efforts to secure peace in the major conflict states of the world. The Liberian crisis which is the subject of this study was one of such cases in which the measures was applied to maintain peace by the Economic Community of West Africa State (ECOWAS). The Liberian crisis which started as an entirely ethnic conflict involving the indigenous ethnic Liberians who constitute the majority of the population and the Afro-America settlers who were settled in Liberia following the abolition of slave trade in America and who have dominated the political scene in the country since their arrival in 1821. The Liberians crisis escalated in 1980 when Samuel Doestaged a coup that brought the ethnic majority of the Liberian to power. The conflict assumed a wider dimension following the involvement of other extraneous forces around Liberians, a situation which the ECOWAS leaders thought would lead to the war spreading to other countries in the sub-region. This study examined the operations of the peacekeeping body- the ECOMOGwhich ECOWAS established for the purpose of securing peace in Liberia. For its explanatory tool, the study adopted the theory of collective Security. The choice of this theory is informed by the fact that it best explains the decision of ECOWAS as a sub-regional body to work for peace within the sub-region. The theory of collective security rest on the assumption that all nations share a primary interest in maintaining International Peace and Security. This work is basically an analytical survey study and in the case it precludes all forms of statistical process in both data collection and data analysis. In this regard, conflict analysis of the mass of data collection from library sources was adopted in the study. The major findings of the study include the fact that the domination of political power by the Afro-America Liberians is at the root of the conflict in the country. The study also discovered that poor funding and the colonial orientations of the various forces contributing states in ECOWAS adversely affected the operation of ECOMOG in Liberia. The study recommends that the Leaders of ECOWAS should establish more integrated peacekeeping forces with training in language and cultures of the Nations in the sub-region.