BACKGROUND: Eating disorders cause significant burden that may be reduced by early and appropriate help-seeking. However, despite the availability of effective treatments, very few individuals with eating disorders seek treatment. Training in mental health first aid is known to be effective in increasing mental health literacy and supportive behaviours, in the social networks of individuals with mental health problems. Increases in these domains are thought to improve the likelihood that effective help is sought. However, the efficacy of mental health first aid for eating disorders has not been evaluated. The aim of this research was to examine whether specific training in mental health first aid for eating disorders was effective in changing knowledge, attitudes and behaviours towards people with eating disorders. METHODS: A repeated measures, uncontrolled trial was conducted to establish proof of concept and provide guidance on the future design of a randomised controlled trial. Self-report questionnaires, administered at baseline, post-training and 6-month follow-up, assessed the effectiveness of the 4-hour, single session, mental health first aid training. RESULTS: 73 participants completed the training and all questionnaires. The training intervention was associated with statistically significant increases in problem recognition and knowledge of appropriate mental health first aid strategies, which were maintained at 6-month follow-up. Sustained significant changes in attitudes and behaviours were less clear. 20 participants reported providing assistance to someone with a suspected eating disorder, seven of whom sought professional help as a result of the first aid interaction. Results provided no evidence of a negative impact on participants or the individuals they provided assistance to. CONCLUSIONS: This research provides preliminary evidence for the use of training in mental health first aid as a suitable intervention for increasing community knowledge of and support for people with eating disorders to seek appropriate help. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry ACTRN12611001181998.