12th International Workshop on Hydrogen Isotopes in Fusion Reactor Materials was held in University of Toyama, Japan, from the 2nd to 4th of June 2014 with participation of 68 researchers from 10 countries. There were 33 oral presentations and 2 tutorial lectures. The workshop dealt with a number of key research topics in the area of hydrogen isotope behavior in fusion reactor materials including hydrogen isotope dissolution, diffusion and trapping, and materials erosion and deposition. The local organizing committee of the workshop appreciates all participants for their attendance, presentations and fruitful discussion.