This book constitutes the refereed conference proceedings of the 12^th EAI International Conference on Quality, Reliability, Security and Robustness in Heterogeneous Networks, QShine 2016, held in Seoul, South Korea, in July 2016. The 27 full papers, 5 short papers and 18 workshop papers were selected from 85 submissions. The papers are organized thematically in tracks, starting with network security, followed by QoS, reliability and modeling, wireless and mobile networks. In addition the papers of two workshops are included: International Workshop on 5G Communication Architecture and Technology (5G-CAT 2016), and the 2nd International Workshop on Sensor Networks and Cloud Computing (SNCC 2016).