The MoDeVVA workshop series brings together researchers and practitioners interested the application of validation and veri cation (V&V) techniques in model-driven engineering (MDE). The main goals of the workshop are to identify, discuss, and elaborate mutual impacts of MDE and V&V. The 12th edition of MoDeVVA took place on the 29th of September 2015 and was co-located with MODELS15 in Ottawa, Canada. After a careful reviewing process with many stimulating discussions, six papers were selected for presentation of the workshop. Each paper was reviewed by at least three members of the program committee. We would like to thank the members of the PC for their support in setting up an interesting program for MoDeVVA.