Objective Nightmares are associated with psychopathology and impaired coping in the general population. However, little is known about this association in a psychiatric population. In this study, we investigate whether patients with diverse psychiatric disorders have increased symptomatology and different coping styles if they suffer from comorbid nightmare disorder. Method Participants were 498 patients with diverse moderate to severe psychiatric disorders. As part of a standard assessment procedure, they filled out questionnaires regarding nightmares, psychopathology, personality pathology, and coping. Results A multivariate analysis of covariance and post hoc tests showed that patients with nightmare disorder scored higher on psychopathology (ηp2 = .03; p = .001) and personality pathology (ηp2 = .01–.03; p < .05). No significant differences were found with regards to coping strategies. Conclusion Nightmare disorder is associated with higher levels of psychopathology and personality pathology in a sample of patients with diverse psychiatric disorders.