This book constitutes the refereed proceedings of the 27th International Workshop on Coordination, Organizations, Institutions, Norms, and Ethics for Governance of Multi-Agent Systems, COINE 2023, held in London, UK, on May 29, 2023 (co-located with 22nd International Conference on Autonomous Agents and Multi-Agent Systems (AAMAS)).This book contains 10 full papers which are the extended and revised versions of the papers accepted to the workshop.The papers were carefully reviewed and selected from 13 submissions. They are organized in topical sections as follows: Norms, Social contracts, Institutions, and Privacy; Studies on the notion of Value; and Argumentation and Conventions