Recent randomized controlled trials indicate that cognitive-behavioral therapy (CBT) for adults with attention-deficit/hyperactivity disorder (ADHD) is an efficacious treatment. Although treatments for adults with ADHD target negative automatic thoughts, there is a lack of empirical evidence demonstrating that such cognitions are associated with ADHD. The goal of this study was to assess the relationship between ADHD and negative automatic thoughts typically associated with depression in a group of adults diagnosed with ADHD (n = 81). Across the sample, self, collateral, and clinician ratings of inattentive ADHD symptom severity, but not hyperactive-impulsive symptom severity, were significantly associated with negative automatic thoughts after considering the role of current depressive symptom severity. Subsequent categorical analyses were conducted by subdividing the ADHD sample into those with (n = 34) and without (n = 47) a comorbid depression diagnosis, and adding a control group (n = 43). Analyses indicated that (a) the ADHD group with comorbid depression reported significantly more negative automatic thoughts than both controls and the ADHD group without comorbid depression, and (b) the ADHD group without comorbid depression reported significantly more negative automatic thoughts than controls. These findings provide an empirical basis for adult ADHD CBT to target negative automatic thoughts, which share a relationship with ADHD even after accounting for the confounding role of depression. Modification of negative automatic thoughts may be a mechanism of change in adult ADHD CBT and should be considered in future research. attention-deficit/hyperactivity disorder | cognitive-behavioral therapy | negative