Social norms are an important influence on health-related behaviours and intention formation. As both suicidal behaviour and non-suicidal self-injury (NSSI) can be motivated by intentions, perceived social norms may have an important role in suicide and NSSI outcomes, although no existing reviews of this association exist. Following the PRISMA Scoping Review extension guidance, a scoping review based on systematic searches of key databases was conducted to identify published English language studies investigating the role of perceived social norms in suicidality and NSSI. Information regarding the types of social norms studied, their relationship to suicidality/NSSI outcomes, study samples and designs was charted. Thirty-six eligible studies (31 quantitative, 4 qualitative, 1 mixed methods) sampling various populations across mostly non-clinical settings were identified and narratively synthesised. Studies varied in how social norms were operationalised, measured, and investigated/explored. Most studies focused on the role of conformity to perceived masculine social norms or to some form of subjective, descriptive, or injunctive norms; there were limited studies on female/feminine norms, pro-social/protective norms, or broader gender/sexuality norms. Most studies (n = 31) were cross-sectional (quantitative) in design, few were based on existing theories of suicide/NSSI or social norms, and none concurrently tested theories of social norms and NSSI/suicidality. Perceived social norms and stronger conformity to norms were generally associated with worse NSSI/suicidality, although some pro-social norms appeared to be protective (e.g., perceived parental norms for adolescents). Whilst conformity to restrictive perceived social norms may be related to poorer suicide and NSSI outcomes, there is a lack of consistency in the literature in how social norms are defined and measured, a lack of theory-based hypothesis testing, and few longitudinal studies. There is a need for more nuanced, theory-based, investigations of how, when, where, why, and for whom, perceived norms have a causal role in NSSI and suicidality outcomes.