This book constitutes the refereed proceedings of the 12th International Conference on Integrated Formal Methods, IFM 2016, held in Reykjavik, Iceland, in June 2016. The 33 papers presented in this volume were carefully reviewed and selected from 99 submissions. They were organized in topical sections named: invited contributions; program verification; probabilistic systems; concurrency; safety and liveness; model learning; SAT and SMT solving; testing; theorem proving and constraint satisfaction; case studies. .