Background: Self-harm prevalence is rising, yet service users encounter stigmatising attitudes and feel let down when they seek professional help. Co-design activities can potentially enable development of more acceptable and effective services. Objectives: To map existing literature describing how people with lived experience of self-harm have engaged in co-designing self-harm interventions, understand barriers and facilitators to this engagement and how meaningfulness of co-design has been evaluated. Inclusion criteria: Studies where individuals with lived experience of self-harm (first-hand or carer) have co-designed self-harm interventions. Methods: In accordance with Joanna Briggs Institute (JBI) scoping review methodology we scoped PubMed, Embase, PsycINFO, Web of Science, Cochrane Library, PROSPERO, ClinicalTrials.gov and relevant websites on 24.12.22. A protocol was published online (http://dx.doi.org/10.17605/OSF.IO/P52UD). Results were screened at title and abstract level, then full-text level by two researchers independently. Pre-specified data was extracted, charted, and sorted into themes. Results: We included twenty co-designed interventions across mobile health, educational settings, prisons, and emergency departments. Involvement varied from designing content to multi-stage involvement in planning, delivery, and dissemination. Included papers described the contribution of 110 female and 26 male co-designers. Few contributors identified as from a minoritized ethnic or LGBTQ+ group. Six studies evaluated how meaningfully people with lived experience were engaged in co-design: by documenting the impact of contributions on intervention design, or through post-design reflections. Barriers included difficulties recruiting inclusively, making time for meaningful engagement in stretched services, and safeguarding concerns for co-designers. Explicit processes for ensuring safety and wellbeing, flexible schedules, and adequate funding facilitated co-design. Conclusions: To realise the potential of co-design to improve self-harm interventions, people with lived experience must be representative of those who use services. This requires processes that reassure potential contributors and referrers that co-designers will be safeguarded, remunerated, and their contributions used and valued.