While comprehensive studies on UN peacebuilding assert that ‘learning has not... been one of the strengths of the United Nations’ (Chesterman 2004, p.256), research so far has largely ignored the UN’s institutional infrastructure for learning. This essay seeks to contribute to closing this gap by surveying the evolution of the UN’s learning infrastructure from the early 1990s to the present. Despite some progress in recent years, the lack of resources, coordination and political will means that turning the UN bureaucracy into a learning organization is unfinished business at best. Rather than focusing all attention on the new Peacebuilding Commission, policymakers and researchers alike should invest additional resources in analysing and strengthening the learning capacity of the UN peacebuilding apparatus.