Background: Research on adults with ADHD has recently identified, in addition to cognitive-executive difficulties, significant impairments in emotion regulation. Objective: This study aimed to assess the efficiency of emotion regulation in adults with ADHD using three strategies: observe, reappraise, and suppress. Method: Adults with ADHD (n = 68) and without ADHD (n = 69) were exposed to neutral or negative IAPS image sets and reported their emotions while employing these strategies. Results: The ADHD group displayed significant emotion dysregulation, depressive symptoms, and anxiety compared to the non-ADHD group. Suppression of negative emotions was shown to be the mechanism by which the ADHD group achieved greater suppression efficiency, although both suppression and reappraisal were equally utilized as regulatory strategies. Conclusion: These results highlight the efficiency of suppression in controlling negative emotions in the ADHD population, while also suggesting potential for effective training in reappraisal.