This book constitutes the proceedings of the 15th German Conference on Multiagent System Technologies, MATES 2017, held in Lepzig, Germany, in August 2017. The 17 full papers presented in this volume were carefully reviewed and selected from 24 submissions for inclusion in the proceedings. Over these 15 years, the MATES conference series has been aiming at the promotion of and the cross-fertilization between theory and application of intelligent agents and multi-agent systems.