This article examines Nigeria’s interventions in the Economic Community of West African States (ECOWAS). Relying on data from key ranking bodies, memoirs of retired career ambassadors, general library materials and thematic data analysis, the study observes that Nigeria’s interventions in ECOWAS have not only been remarkable, they have also allowed the country to consolidate its position as the undisputed leader in West Africa. While the platform of ECOWAS has allowed Nigeria to pursue some noble objectives, there are some inconveniences associated with this policy orientation. These contradictions, which have sometimes constrained Nigeria’s diplomacy in West Africa and contracted the returns, include the anti-Nigerian sentiments from some Francophone members of ECOWAS, occasional unfriendly attitude of some small West African countries, and Nigeria’s worsening security challenges that are now spilling into neighbouring countries. Appropriate policy measures are also provided to counteract these contradictions.