BACKGROUND: Autistic people with co-occurring attention deficit/hyperactivity disorder (ADHD) appear to be at heightened risk of suicide. To understand why, we explored two explanatory mechanisms from the interpersonal theory of suicide: first, that co-occurring ADHD might be associated with greater risk through greater thwarted belongingness and perceived burdensomeness and, secondly, that hyperactive/impulsive features might incur additional risk through their association with painful and provocative events, which are suggested to create "capability" for suicide. METHODS: Autistic adults (n = 314) completed an online survey including measures of thwarted belongingness, perceived burdensomeness, painful and provocative events, acquired capability for suicide, and ADHD features. Creating an overall index of likely ADHD, we examined associations between likely ADHD, suicide ideation, and lifetime suicide attempts through the parallel mediators of thwarted belongingness, perceived burdensomeness, anxiety, and depression. In several models, we then examined hyperactive, impulsive, and inattentive features as predictors of exposure to painful and provocative events and subsequent capability for suicide, and examined whether these two variables, sequentially or individually, mediated an association with lifetime suicide attempts. RESULTS: Likely ADHD was associated with past-year suicide ideation through greater depression and perceived burdensomeness, which also mediated its association with more suicide attempts. Hyperactive and impulsive features were associated with exposure to painful and provocative events and through this acquired suicide capability. Both features were associated with more numerous suicide attempts through these two mediators sequentially, and through exposure to painful and provocative events alone. CONCLUSIONS: These data suggest that suicidality in autistic people with ADHD may be partially related to perceived burdensomeness and to acquired suicide capability after exposure to painful and provocative events. However, as we observed a pathway to suicidality associated with painful and provocative events alone, it is likely that there are also other explanatory mechanisms for the influence of traumatic events on suicide risk.