For decades, personality was thought to be a set of stable characteristics. However, in the dimensional approach, personality traits are considered to vary on a continuum. This retrospective cohort study examines changes in personality traits, as measured by the NEO Five Factor Inventory, in anxiety-disordered inpatients. Paired sample T-test analyses are used to measure trait differences before and after treatment. Analyses of variance are applied to measure the influence of diagnosis on personality change, and regression analyses to investigate if the 90-item symptom checklist symptom reduction predicts personality trait changes. Results show that patients become less neurotic and more extravert at post-measurement, supported by large to medium effect sizes, and are not influenced by diagnostic category. Only 30% and 21% of the change in neuroticism and extraversion respectively, is explained by symptom reduction. It is concluded that personality traits neuroticism and extraversion can change over time in anxious inpatients while changes are not a direct consequence of a mood-state effect (symptom reduction). Results are compatible with a dimensional conceptualization of psychopathology, which will be incorporated in the future edition of the Diagnostic and Statistical Manual for Mental Disorders (DSM-V). Copyright © 2010 John Wiley & Sons, Ltd.