Attention deficit hyperactivity disorder (ADHD) is one of the most prevalent chronic neuropsychiatric disorders, severely affecting the emotional well-being of children as well as of adults. It has been suggested that individuals who experience symptoms of ADHD develop maladaptive schemata of failure, impaired self-discipline, social isolation, and shame. These schemata may then contribute to impaired emotional well-being by increasing unhelpful responses to stressful life events. However, to date, no empirical research has tested this theoretical proposition. In a sample of 204 nonclinical adults, we conducted a serial multiple mediator analysis, which supported the proposed model. More severe ADHD symptoms were associated with higher levels of perceived stress both directly and indirectly through stronger maladaptive schemata, which, in turn, were related to lower levels of emotional well-being. Results suggest that identifying and modifying maladaptive schemata may be an important addition to psychotherapy for adult ADHD patients.