Background & Objectives: Terror catastrophizing, defined as an ongoing fear of future terrorist attacks, is associated with a higher incidence of anxiety disorders, among other psychological impacts. However, previous studies examining terror catastrophizing's relationship to other mental health disorders are limited. The current study sought to determine if patients diagnosed with anxiety and depression would experience increased terror catastrophizing. Additionally, this study aimed to investigate whether parental terror catastrophizing increases children's internalizing symptoms.Design & Methods: Individuals were randomly drawn from the Danish Civil Registration System and invited to complete a series of questionnaires to measure terror catastrophizing tendency, lifetime parental trauma, and children's internalizing symptoms. In total, n = 4,175 invitees completed the survey of which 933 reported on a child between 6 and 18 years. Responses were analyzed using a generalized linear regression model.Results: Participants diagnosed with anxiety alone or comorbid with depression were more likely to experience symptoms of terror catastrophizing than undiagnosed participants (β = 0.10, p < .001; β = 0.07, p = .012). Furthermore, the parental tendency to catastrophize terror was associated with higher internalizing symptoms in children (β = 0.09, p = .006), even after taking parental diagnoses, as well as lifetime and childhood trauma into account.Conclusion: The results can inform clinical practices to account for a patient's potential to exhibit increased terror catastrophizing tendencies or be more affected by traumatic events. Additionally, they can offer insights for designing novel preventative interventions for the whole family, due to the relation between parental tendencies for terror catastrophizing and the internalizing symptoms observed in children.