Abstract Background Given the high prevalence of mental disorders and the comparatively low rate of professional help-seeking, it is useful for members of the public to have some skills in how to assist people developing mental disorders. A Mental Health First Aid course has been developed to provide these skills. Two randomized controlled trials of this course have shown positive effects on participants' knowledge, attitudes and behavior. However, these trials have provided limited data on participants' subsequent experiences in providing first aid. To remedy this, a study was carried out gathering stories from participants in one of the trials, 19–21 months post-training. Methods Former course participants were contacted and sent a questionnaire either by post or via the internet. Responses were received from 94 out of the 131 trainees who were contacted. The questionnaire asked about whether the participant had experienced a post-training situation where someone appeared to have a mental health problem and, if so, asked questions about that experience. Results Post-training experiences were reported by 78% of respondents. Five key points emerged from the qualitative data: (1) the majority of respondents had had some direct experience of a situation where mental health issues were salient and the course enabled them to take steps that led to better effects than otherwise might have been the case; (2) positive effects were experienced in terms of increased empathy and confidence, as well as being better able to handle crises; (3) the positive effects were experienced by a wide range of people with varied expectations and needs; (4) there was no evidence of people over-reaching themselves because of over-confidence and (5) those who attended were able to identify quite specific benefits and many thought the course not only very useful, but were keen to see it repeated and extended. Conclusion The qualitative data confirm that most members of the public who receive Mental Health First Aid training subsequently provide support to people with mental health problems and that this support generally has positive effects.