The relationship between the dimensional assessment of personality and difficulties in emotion regulation has yet to be made clear. The present study aimed to investigate the role of personality traits and emotion regulation on personality functioning. Difficulties in Emotion Regulation Scale (DERS), Beck Anxiety Inventory, Beck Depression Inventory, Personality Inventory for DSM-5 (PID-5) and Level of Personality Functioning Scale (LPFS) were rated for 220 patients with depression and/or anxiety disorder diagnosis and 100 healthy controls. Stepwise regression analyses (SRA) were used to find potential predictors of personality functioning, and generalized linear analyses (GLA) were used to find mediators between the traits and personality functioning. SRA results in the clinical group showed that higher depression, antagonism, difficulties in impulse control and difficulties in awareness predicted higher levels of dysfunction in personality. According to GLA results in the clinical group, the impulse subscale of DERS partially mediated the relationship between antagonism and level of impairment in personality functioning. Our results indicate that certain emotion regulation styles and personality traits play an important role in predicting personality functioning in the clinical sample of depression and anxiety patients. Future studies should focus on specific emotion dysregulation strategies and broaden the dimensional personality literature in different samples.