Environmental sustainability is a new and fast moving field in health. There is little evidence about how to teach it effectively to health professionals. Methods: We conducted a pilot study of an educational intervention with more than 200 UK public health registrars. The intervention consisted of a day-long workshop with the aim of training participants to help make the UK’s National Health Service more environmentally sustainable. Results: We measured outcomes in three areas: awareness, advocacy and actions. Comparison of baseline and post intervention questionnaire scores showed statistically significant improvements in the awareness and advocacy scores. Actions were assessed qualitatively. Our findings suggest that, while there are some pockets of good practice, many health professionals are yet to engage with sustainability in the workplace. Discussion: We propose reasons why health professionals are yet to become involved in sustainability issues despite the related opportunities for health and health services.