This book constitutes the refereed proceedings of the 23rd IFIP WG 6.1 International Conference on Coordination Models and Language, COORDINATION 2021, held in Valletta, Malta, in June 2021, as part of the 16th International Federated Conference on Distributed Computing Techniques, DisCoTec 2021.The 15 regular papers, 2 short papers, and 1 tutorial paper presented in this book were carefully reviewed and selected from 31 submissions. COORDINATION provides a well-established forum for the growing community of researchers interested in coordination models and languages, architectures, verification and implementation techniques necessary to cope with the complexity induced by the demands of today's software development.The tool papers describe experience reports, technological artefacts, and innovative prototypes, as well as educational tools in the scope of the research topics of the conference.Due to the Corona pandemic this event was held virtually.