Background Personality disorders are a multi-theoretical construct that encompasses predictable and quantifiable behavioral, cognitive, and affective characteristics in individuals. Previous studies underscore the existence of a relationship between personality disorders and defense mechanisms, these being coping styles that arise unconsciously in the face of adversity and that have adaptive purposes. There is evidence that alludes to a connection between pathological personality, defense mechanisms, and their relationship with negative mental health outcomes, such as depressive and anxious symptoms. The objective of this study was to study, psychometrically measure, and associate personality disorders, defense mechanisms, and depressive and anxious symptoms. Methodology A cross-sectional study was conducted on 81 participants with major depressive disorder, generalized anxiety disorder, and panic disorder who received treatment at a tertiary care institution between July 2021 and February 2022. Psychometric instruments were employed to evaluate the study variables, such as the Beck Depression Inventory (BDI), the Hamilton Depression Rating Scale (HAM-D), the Hamilton Anxiety Rating Scale (HAM-A), the Personality Diagnostic Questionnaire - Version 4 (PDQ-4) Plus, and the 40-item Defensive Styles Questionnaire (DSQ-40). Results Depressive and anxious symptoms were related to the scores obtained in the Defensive Styles Questionnaire and the Personality Disorders Questionnaire. Some defense mechanisms were positive predictors of the score between these scales. Conclusions There is a relationship between personality traits and defense mechanisms that could influence the development and severity of depressive and anxious psychopathology in this population.