Little is known about whether mental health first aid knowledge and beliefs of young people actually translate into actual behavior. This study examined whether young people s first aid intentions and beliefs predicted the actions they later took to help a close friend or family member with a mental health problem. Participants in a 2006 national survey of Australian youth (aged 12-25. years) reported on their first aid intentions and beliefs based on one of four vignettes: depression, depression with alcohol misuse, psychosis, and social phobia. At a two-year follow-up interview, they reported on actions they had taken to help any family member or close friend with a problem similar to the vignette character since the initial interview. Of the 2005 participants interviewed at follow-up, 608 reported knowing someone with a similar problem. Overall, young people s first aid intentions and beliefs about the helpfulness of particular first aid actions predicted the actions they actually took to assist a close other. However, the belief in and intention to encourage professional help did not predict subsequent action. Findings suggest that young people s mental health first aid intentions and beliefs may be valid indicators of their subsequent actions.