Self-disclosure, referring to the ability to communicate and share intimate personal feelings, has strong face validity for many young people as a way of improving anxiety and depression outcomes. The current review aimed to generate the first comprehensive evidence synthesis of self-disclosure interventions involving young people aged 14-24 years who are either disclosers or recipients of personal information about living with anxiety and/or depression. A systematic review of quantitative and qualitative data was combined with new insights from an adolescents and young adults lived-experience panel (n = 7) with the intention to combine rigorous systematic review methods and experiential knowledge. Six studies of variable quality were included in this review, five were quantitative and one was qualitative. Findings suggest that self-disclosure may be effective at reducing symptoms for adolescents and young adults with established depression; effects were not apparent when delivered as early prevention. No evidence for impacts on anxiety was found. The potential for negative effects like bullying or harassment was identified. Findings were limited by a small number of studies; low representation of peer-reviewed studies from low-or middle-income countries; and varied interventions in terms of format, participants' context, and nature of delivery. Self-disclosure may be of value in the context of interventions intended explicitly to reduce depression for those already showing symptoms. Delivery by non-specialists (such as peers and teachers) in addition to mental health professionals can help build capacity in community health systems. Self-disclosure may also be helpful at reducing stigma and stimulating help-seeking at earlier stages of mental health problems.