This book constitutes the proceedings of the 20th International Conference on Coordination Models and Languages, COORDINATION 2018, held in Madrid, Spain, in June 2018, as part of the 13th International Federated Conference on Distributed Computing Techniques, DisCoTec 2018. The 12 full papers included in this volume were carefully reviewed and selected from 26 submissions. The papers cover a wide range of topics and techniques related to system coordination, including: actor-based coordination, tuple- based coordination, agent-oriented techniques, constraints- based coordination, and finally coordination based on shared spaces.