Introduction Young people with eating disorders are at risk of harm to their social, emotional and physical development and life chances. Although they can be reluctant to seek help, they may access social media for information, advice or support. The relationship between social media and youth well‐being is an emotive subject, but not clearly understood. This qualitative study aimed to explore how young people used a youth‐orientated, moderated, online, eating disorders discussion forum, run by an eating disorders charity. Methods We applied a netnographic approach involving downloading and thematically analysing over 400 messages posted August–November 2012. Results Data analysis generated five themes: Taking on the role of mentor; the online discussion forum as a safe space; Friendship within the online forum; Flexible help; and Peer support for recovery and relapse prevention. Forum moderation may have influenced the forum culture. Discussion Our findings are consistent with literature about youth preferences for mental health self‐care support. A young person's decision to use this discussion forum can be construed as pro‐active self‐care. A moderated online discussion forum can make a positive contribution to support for youth with eating disorders, countering negative media perceptions of online groups. Conclusion This study adds to knowledge about how young people access support via social media. Online discussion forums can be safe and acceptable spaces for youth to access help. Further research could provide insights into the impact of forum moderation.