BACKGROUND: Many members of the public have poor mental health literacy. A Mental Health First Aid training course was developed in order to improve this. This paper describes the training course and reports an evaluation study looking at changes in knowledge, stigmatizing attitudes and help provided to others. METHODS: Data are reported on the first 210 participants in public courses. Evaluation questionnaires were given at the beginning of courses, at the end and at 6 months follow-up. Data were analyzed using an intention-to-treat approach. RESULTS: The course improved participants' ability to recognize a mental disorder in a vignette, changed beliefs about treatment to be more like those of health professionals, decreased social distance from people with mental disorders, increased confidence in providing help to someone with a mental disorder, and increased the amount of help provided to others. CONCLUSIONS: Mental Health First Aid training appears to be an effective method of improving mental health literacy which can be widely applied.