People with co-occurring substance use and mental health conditions experience disproportionately high levels of suicidal ideation, attempts and deaths compared with those with either condition alone, yet guidance for suicide risk formulation in this group is limited. This integrative literature review synthesised evidence on suicidality in adults with co-occurring conditions, identified risk and protective factors, and refined risk formulation approaches for mental health nursing. Using Whittemore and Knafl's methodology and Toronto and Remmington's stepwise guidance, CINAHL, Embase, Medline and PsycInfo were searched without date limits. Empirical studies of adults with co-occurring substance use and mental health conditions were included, alongside relevant grey literature; specialist populations (e.g., prison, veteran, neurological/developmental) were excluded. Thirty-three quantitative studies and six grey literature sources (total n = 39; 35 883 participants across 19 countries) were appraised using Critical Appraisal Skills Programme tools and the AACODS checklist. Co-occurring conditions were consistently associated with elevated suicidality, especially mood disorders, notably depression, combined with alcohol use disorder. Risk factors were mapped onto an extended 5Ps model: presenting, predisposing, precipitating, perpetuating and protective domains, with an additional Patient Experience domain to capture barriers to care, service dissatisfaction and stigma. Protective factors were comparatively scarce. Applying the Integrated Motivational-Volitional model highlighted psychological processes, including mental pain, perceived burdensomeness, impulsivity and access to means, that may contribute to suicidal behaviour. For mental health nurses and other mental health professionals, incorporating patient experience and IMV-informed processes into an extended 5Ps framework may support more thorough suicide risk formulation and the development of safety and treatment plans that promote safer, more equitable and integrated care for people with co-occurring conditions.