This special issue of the Formal Aspects of Computing journal contains a selection of the best papers accepted at the 12 th edition of the international conference series on Software Engineering and Formal Methods (SEFM). This conference was held in Grenoble (France) on September 1-5, 2014. The aim of the conference was to bring together practitioners and researchers from academia, industry and government to advance the state of the art in formal methods, to scale up their application in the software industry and to encourage their integration with practical engineering methods. The SEFM'14 conference received 106 full submissions, and the programme committee of the conference decided to accept 29 papers. Out of these 29 papers, we selected the best six papers, and the authors of these papers were invited to submit a revised and extended version of their work to this special issue. After a meticulous review process, we finally accepted five of the six invited papers. The topics covered in this special issue are the following: Domain Specific Languages, Component-based Systems and Architectures, Learning Finite State Machines, Construction and Verification of Imperative Programs, and Partial Order Reduction in the context of Model Checking.