Youth suicide is a significant public health problem. A systematic review was conducted to examine the effectiveness of school, community and healthcare-based interventions in reducing and preventing suicidal ideation, suicide attempts and deliberate self-harm in young people aged 12–25 years. PsycInfo, PubMed and Cochrane databases were searched to the end of December 2014 to identify randomised controlled trials evaluating the effectiveness of psychosocial interventions for youth suicide. In total, 13,747 abstracts were identified and screened for inclusion in a larger database. Of these, 29 papers describing 28 trials fulfilled the inclusion criteria for the current review. The results of the review indicated that just over half of the programs identified had a significant effect on suicidal ideation (Cohen’s d = 0.16–3.01), suicide attempts (phi = 0.04–0.38) or deliberate self-harm (phi = 0.29–0.33; d = 0.42). The current review provides preliminary support for the implementation of universal and targeted interventions in all settings, using a diverse range of psychosocial approaches. Further quality research is needed to strengthen the evidence-base for suicide prevention programs in this population. In particular, the development of universal school-based interventions is promising given the potential reach of such an approach.