This book constitutes the refereed proceedings of the 12th International Conference on Formal Engineering Methods, ICFEM 2010, held in Shanghai, China, November 2010. The 42 revised full papers together with 3 invited talks presented were carefully reviewed and selected from 114 submissions. The papers address all current issues in formal methods and their applications in software engineering. They are organized in topical sections on theorem proving and decision procedures, web services and workflow, verification, applications of formal methods, probability and concurrency, program analysis, model checking, object orientation and model driven engineering, as well as specification and verification.