Teacher education is widely recognised as a key strategy that is yet to be effectively utilised to embed environmental education and/or education for sustainability in schools. This paper reports on a research study that examined a range of pre-service teacher education initiatives, both in Australia and internationally, that were seeking to reorient teacher education towards environmental sustainability. This paper reports on six factors utilised across the initiatives that were critical to their success. These were (1) the nature and length of funding arrangements; (2) the range and quality of partnerships and networks; (3) the curriculum focus and the teaching and learning processes used; (4) the nature of, and incentives for, participant engagement; (5) the level at which a change was being sought; and (6) the use of evaluation as a tool for learning and ongoing improvement. This paper discusses why and how each of these six factors proved critical and explores the implications for initiatives seeking to reorient teacher education towards environmental sustainability.