The contemporary global system is characterised by the presence of a multitude of International Organisations (IOs) whose relevance is sustained by the roles they play. Among these IOs, the United Nations (UN) is of paramount importance as a result of its universal membership and extensive mandate. Its international role is influenced by its evolving structures, practices and goals. Among its most recent objectives are the Millennium Development Goals (MDGs) which address the challenge of holistic human development at the global level. This study aims to assess the UN’s role in pursuing the MDGs as they relate to the development of children in West Africa. The first two of the eight goals have been selected for the purpose of focusing the research, namely the eradication of extreme poverty and hunger, and the elimination of illiteracy by achieving universal primary education. Children, who bear the brunt of global underdevelopment and whose development is a key element in breaking cycles of poverty, are the focus of the study. The general and historical role played by the UN in advancing child development is therefore assessed with regards to the issue-fields indicated by the two selected MDGs. Specific application is then done in the case of West Africa, chosen as case study because the region is the poorest in the world and arguably indicative of most urgent MDG focus. Clive Archer’s analytical outline, which depicts IOs variously as instruments, arenas and actors, is used as a conceptual framework. Archer contends that IOs can be utilised as instruments by other global actors, serve as arenas for dialogue and cooperation among such actors and also assume proactive, independent identities as actors in pursuit of specific objectives. The study concludes that Archer’s framework is relevant, but that the existence of all three roles in the same functional space has notable and often contradictory implications. While the UN generally plays its roles as actor and arena in achieving its first two MDGs among West African children with relative ease, its role as instrument is dependent on the agendas and political will of other actors in the global system. Notwithstanding the weakness of its role as instrument, however, the UN’s triad of roles towards the development of children, and specifically children in West Africa, is a key element of the organisation’s global relevance.