In the past decade the humanitarian system has had to respond to natural disasters and complex emergencies of increasing severity. In 2005, as an attempt to increase coordination amongst humanitarian actors and improve coherence in humanitarian response, the United Nations implemented a coordination mechanism called the Cluster Approach. The aim of this paper is to present common challenges of the Cluster Approach raised since its implementation and to provide lessons learned, based on the findings of a meta-analysis of 18 existing case studies, evaluations, and literature. The paper assesses progress the Cluster Approach has made toward meeting its intended goals, exposing different stakeholder perspectives and aggregating findings from various clusters and country contexts.