This book constitutes the proceedings of the 5th IPM International Conference on Fundamentals of Software Engineering, FSEN 2013, held in Tehran, Iran, in April 2013. The 17 full papers presented in this volume were carefully reviewed and selected from 65 submissions. The topics of interest in FSEN span over all aspects of formal methods, especially those related to advancing the application of formal methods in software industry and promoting their integration with practical engineering techniques.