This study examines the relationship between Community-Based Organizations (CBOs) and marine and coastal resource management in the Western Indian Ocean Region. It explores what roles CBOs play in relation to natural resource utilisation and whether they have an ability to act effectively as community managers of these resources. The research focuses on CBOs in the coastal zone of Kenya and Tanzania. The study identified how the lack of legal mandate conferred on CBOs (except Beach Management Units, Community Forestry Associations and Kamati ya Mazingira) can severely constrain their capacity to act and authority in relation to NRM. Manipulation and corruption can also cause CBO leadership to betray communities when it comes to making decisions about resource use. In short, this study finds that there are examples of excellent practice and leadership by CBOs in relation to NRM. However, internal CBO capacity is very limited and the external political economy imposes severe constraints on CBOs ability to act as effective natural resource managers.