There is a need for effective and youth-friendly approaches to suicide prevention, and social media presents a unique opportunity to reach young people. Although there is some evidence to support the delivery of population-wide suicide prevention campaigns, little is known about their capacity to change behaviour, particularly among young people and in the context of social media. Even less is known about the safety and feasibility of using social media for the purpose of suicide prevention. Based on the #chatsafe guidelines, this study examines the acceptability, safety and feasibility of a co-designed social media campaign. It also examines its impact on young people's willingness to intervene against suicide and their perceived self-efficacy, confidence and safety when communicating on social media platforms about suicide. A sample of 189 young people aged 16-25 years completed three questionnaires across a 20-week period (4 weeks pre-intervention, immediately post-intervention, and at 4-week follow up). The intervention took the form of a 12-week social media campaign delivered to participants via direct message. Participants reported finding the intervention acceptable and they also reported improvements in their willingness to intervene against suicide, and their perceived self-efficacy, confidence and safety when communicating on social media about suicide. Findings from this study present a promising picture for the acceptability and potential impact of a universal suicide prevention campaign delivered through social media, and suggest that it can be safe to utilize social media for the purpose of suicide prevention.