Aim This study investigated the prevalence and odds of suicide attempts among adults with attention deficit hyperactivity disorder (ADHD) compared to those without and identified factors associated with suicide attempts among adults with ADHD. Methods Secondary analysis of the nationally representative Canadian Community Health Survey–Mental Health (CCHS-MH) (n = 21,744 adults, of whom 529 had ADHD). Respondents were asked whether they received an ADHD diagnosis from a health care professional. Lifetime suicide attempt was based on self-report. Results Adults with ADHD were much more likely to have attempted suicide than those without (14.0% vs. 2.7%). One in four women with ADHD have attempted suicide. Sixty percent of the association between ADHD and attempted suicide was attenuated when lifetime history of depression and anxiety disorders were taken into account. Female gender, lower education attainment, substance abuse, lifetime history of depression, and childhood exposure to chronic parental domestic violence were found to be independent correlates of lifetime suicide attempts among those with ADHD. Conclusion These findings can inform targeted screening and outreach to the most vulnerable adults with ADHD.