ABSTRACT: Importance:Catastrophizing is a maladaptive thought process that involves irrational fear and worry about anticipated or actual symptoms. Although clinically relevant, the role of catastrophizing in patients with chronic dizziness or imbalance has not yet been explored to our knowledge. Objectives:To validate a measure of dizziness catastrophizing and to assess its association with dizziness-related disability compared with other negative affect constructs (eg, anxiety and depression). Design, Setting, and Participants:For this retrospective medical record review, the Dizziness Catastrophizing Scale (DCS), a dizziness-specific catastrophizing assessment tool, was adapted from the previously validated Pain Catastrophizing Scale. Psychometric evaluation of the DCS was performed. In addition, the associations of dizziness catastrophizing and positive and negative affectivity with dizziness-related disability were assessed using structural equation modeling and regression analyses. Data were collected using a retrospective medical record review from April 27, 2010, to June 25, 2014. The dates of analysis were June 3 to August 15, 2017. The setting was the Multidisciplinary Neurotology Clinic at the Toronto General Hospital (Toronto, Ontario, Canada). Participants were 457 adult outpatients with dizziness or imbalance who were referred to the clinic. Main Outcomes and Measures:Psychometric properties of the DCS and its association with dizziness-related disability, as measured with the Dizziness Handicap Inventory. Results:Among 457 patients (mean [SD] age, 53.4 [15.4] years; 154 [33.7%] male), the DCS demonstrated good convergent (r = 0.78, P < .001) and discriminant validity (r = -0.40, P < .001) with the negative and positive affectivity, respectively; internal consistency (α = .95); and test-retest reliability (intraclass correlation coefficient, 0.92; P < .001 at the 95% CI). An exploratory dimension reduction analysis revealed a single latent component of the DCS. The results of the structural equation modeling and regression analyses revealed that dizziness catastrophizing, although associated with negative affectivity (eg, symptoms of anxiety and depression), was independently associated with dizziness-related disability (standardized β = 0.378; P < .001). Furthermore, a strong association was found between catastrophizing and dizziness-related disability across different dizziness-related diagnoses (r ≥ 0.6; P < .001). Conclusions and Relevance:In this study, the DCS was a valid and reliable measure for evaluating catastrophic thinking in patients with dizziness, which was independently associated with dizziness-related disability. Future studies should investigate the influence of alleviating symptoms of catastrophizing on functional outcomes in patients with dizziness or imbalance, the results of which will help guide novel approaches to the clinical care of patients with chronic dizziness.