Background: Research indicates substantial co-occurance of personality pathology and hypochondriasis, which both involve significant psychosocial impairment. Objective: This study sought to investigate the role of personality pathology for explaining functional impairment in patients with hypochondriasis, while accounting for the influence of health anxiety severity. Methods: Patients diagnosed with hypochondriasis (N = 84; 60% women) were administered interview- and self-report instruments for personality pathology, health anxiety severity, and functional impairment (general, social, and physical): The Structured Clinical Interview for DSM-IV Axis II (SCID-II), the Personality Inventory for DSM-5 (PID-5), the Short Health Anxiety Inventory (SHAI), the 36-item Short Form health survey (SF-36), and the Global Assessment of Functioning (GAF). Hierarchical regression analyses were performed with boot-strapping (1000 samples). Results: Findings overall showed that personality pathology incrementally explained functional impairment over the influence of health anxiety severity. More specifically, findings revealed that the incremental effect of PID-5 trait dimensions was substantially larger than the SCID-II personality disorder criterion-count. Functional impairment was specifically associated with SCID-II symptoms of Avoidant Personality disorder and dependent personality disorder as well as PID-5 trait domains of negative affectivity, detachment, and psychoticism. Conclusions: The findings highlight the potential significance of personality pathology for understanding and clinical management of functional impairment in patients with hypochondriasis. The personality features that best explained functional impairment were avoidant personality disorder and dependent personality disorder and, in particular, DSM-5 and the International Classification of Diseases, 11th revision personality trait domains of negative affectivity, detachment, and psychoticism.