This book constitutes the refereed conference proceedings of the 12th International Conference on Security and Privacy in Communications Networks, SecureComm 2016, held in Guangzhou, China, in October 2016. The 32 revised full papers and 18 poster papers were carefully reviewed and selected from 137 submissions. The papers are organized thematically starting with mobile and network security, followed by applied cryptography, web security and privacy, system security, hardware security. The volume also includes papers from the ATCS workshop and the poster session.