This chapter focuses on the designing and development of blended learning environments for adult education, and especially the education of teachers. The author argues that the best combination of advanced learning technologies of synchronous and asynchronous learning is conducive to the formation of new learning environments, which, under certain pedagogical conditions, will adequately meet the special needs of adult students. Particular emphasis is given to the designing and development of a pedagogical blended learning model based on the principles of transformation adult theory and constructivism. This model implements advanced learning technologies in a pedagogical context, aiming at the formation of a collaborative blended learning environment, which will encourage critical thinking and reflection, providing the necessary conditions for a polymorphic distant education for teachers. Finally, we present a case study of a blended environment of teachers’ training designed by the Center of Intercultural and Migration Studies (E.DIA.M.ME.) at the University of Crete.