The present research is embedded in the professional development and research line and in the needs of secondary education and first-year university teachers. We focussed on evidencing the importance of teachers’ professional training to include some specific adaptation and skills in intercultural dialogue and understanding -often called Intercultural Competence- because of its direct impact on the sustainable development of human beings, groups, and ecosystems. We investigated the role played by each of the main competencies linked to the following intercultural dimensions: Professional Identity, Ethics and Axiology, Methodology, and Inclusive Education. We used an integrated methodology and a cross-study of data, performed after the obtention of a three-cornered evaluation of results collected in focus groups, interviews, and questionnaires. We were able to show the impact of intercultural dialogue and understanding in the education for a sustainable development pattern. This is fundamental to set up a new ecology of forms, knowledge, attitudes, and educational meanings, further used to update teachers and students’ training in sustainable ecology and cultural diversity. Progress made in these complementary competencies -Professional Identity, Ethics and Axiology, Methodology- were appraised by teachers participating in the present study; the latter showing an increased interest and demand for the intercultural competence, after increasing their proficiency in the other complementary competencies.