Description:This book constitutes the thoroughly refereed post-workshop proceedings of the International Workshop on Coordination, Organization, Institutions and Norms in Agent Systems, COIN 2007, held as two events at AAMAS 2007, the 6th International Joint Conference on Autonomous Agents and Multiagent Systems in Honolulu, HI, USA, in May 2007 and MALLOW 2007, the Federated Workshops on Multi-Agent Logics, Languages, and Organisations in Durham, UK, in September 2007. This volume is the third in a series focussing on issues in Coordination, Organizations, Institutions and Norms (COIN) in multi-agent systems. The 23 papers in this volume are revised versions of papers presented at the two workshops that were carefully selected from 38 initial submissions. The papers are organized in topical sections on coordination, organization and institutions, and norms.