This report describes the activity and characteristics of individuals who engage with Beyondblue’s Suicidal thoughts and self-harm online forum to provide an evidence base for improving and replicating these services for people vulnerable to serious mental health risks. The report demonstrates there is a deep need, and great capacity for supportive conversations among peers which can be facilitated by online community platforms. Members of this forum were younger than members of Beyondblue's forums as a whole, (15-34-years-old compared with 35-54-years-old than for overall forums). New members most often posted threads at times of crisis, with a focus on ‘not coping’, or feeling ‘lost’ or ‘hopeless’, and present with multiple concurrent and long-term mental health issues; with relationships central to their concerns. Supportive interactions were led and maintained by a minority of key intermediaries or peer mentors, many, but not all of whom have taken on an official role as Community Champion. The overall impact of the forum and influence of supportive participants and peer mentors demonstrated evidence of positive behaviour change.