BackgroundDespite an overall national decline in violent crime, weapon carrying and serious violence among youth appears to be rising. Following the example of successful programmes taking a public health approach to violence, such as that in Glasgow (UK), we aimed to review the global evidence base to inform the development of the serious youth violence strategy for the London Borough of Lambeth (UK). MethodsThis narrative review examined evidence for key factors involved in youth violence, effective preventative interventions (using a thematic approach), shared characteristics of effective interventions, and key principles used by successful interventions or programmes in order to inform Lambeth's approach. Evidence was found through programme websites, clearing houses, and databases (National Health Service Healthcare Databases Advanced Search, Trip, and Social Survey Research Intervention using variations on “youth”, “violence”, and “prevention”, for evidence published between 2013 and 2018 in English). FindingsMore than 30 different risk and protective factors were found to be strongly associated with youth violence. Factors are often age-specific: family factors including adverse childhood events are crucial in early childhood, whereas individual factors (eg, conduct disorders or substance misuse) have a greater role in adolescence. 28 effective and ten promising intervention themes were found: most focused on effective parenting or childhood skills development, constituting primary prevention. Despite evidence suggesting greater cost effectiveness, fewer secondary and tertiary prevention intervention types were found. There was a substantial gap in the evidence for interventions targeting gang-related violence. Key characteristics, such as enhancing protective factors, mitigating risk factors, working in the natural environments of youth, and use of trained facilitators, are shared by effective interventions. Many successful programmes have demonstrated that strong community partnerships, targeting of multiple risk and protective factors, and robust monitoring and evaluation mechanisms might be important determinants of success. InterpretationA comprehensive programme for preventing youth violence, across different levels of prevention and tackling multiple areas of need, should be designed in partnership with the local community. There are many effective interventions that could be implemented in Lambeth, ensuring fidelity to the original specification; promising interventions could be implemented if they match specific local needs. When it is not possible to match an evidence-based intervention to an area of need, the substantial evidence on key characteristics of successful interventions should be used to innovate at a local level, with robust mechanisms for monitoring and evaluation. FundingNone.