This book constitutes the thoroughly refereed post-conference proceedings of the 11th International Workshops on Coordination, Organizations, Institutions and Norms in Agent Systems, COIN 2015. The workshops were co-located with AAMAS 2015, held in Istanbul, Turkey, in May 2015, and with IJCAI 2015, held in Buenos Aires, Argentina, in July 2015. The 23 full papers were carefully reviewed and selected from 46 initial submissions for inclusion in this volume. The papers cover a wide range of topics from work on formal aspects of normative and team based systems, to software engineering with organizational concepts, to applications of COIN based systems, and to philosophical issues surrounding socio-technical systems. They highlight not only the richness of existing work in the field, but also point out the challenges and exciting research that remains to be done in the area.