The Workshop on Secure Network Protocols (NPSec) is a top workshop focusing on cutting-edge research with a broad range of topics related to secure network protocols. NPSec 2015 is a one- day event held in conjunction with the 23d IEEE International Conference on Network Protocols (ICNP 2015). NPSec 2015 will focus on two exciting areas related to secure network protocols. First, development and analysis of networking protocols for the secure operation of various network infrastructures, including both today’s Internet and future Internet architectures, wireless and mobile networking, cloud-based networking, and P2P and overlay networks. Papers about new secure protocols, security enhancements to existing protocols, or protocol analysis (such as new attacks on existing protocols) are welcome. Second, employing such secure network protocols to create or enhance network applications, especially those in new and emerging areas, such as support for the Internet of Things, vehicular networks, and software defined networks.