This book constitutes the refereed proceedings of the 15th International Conference on Software Engineering and Formal Methods, SEFM 2017, held in Trento, Italy, in September 2017. The 17 full papers and 6 short papers presented were carefully reviewed and selected from 102 submissions. The papers deal with a large range of topics in the following research areas: new frontiers in software architecture; software verification and testing; software development methods; application and technology transfer; security and safety; an d design principles. .