Research supported that people with borderline personality disorder (BPD), or BPD features had higher attachment insecurity, psychological symptoms, and impairments in mentalizing compared to non-clinical controls. Yet, little is known about the mediational link from attachment to psychological symptoms via mentalizing dimensions in BPD. The aim of this study was to test a moderated mediation model where BPD features moderated the mediation model of attachment, mentalizing, psychological symptoms. In the study, 516 participants aged between 18 and 35 from the general population completed the Parental Bonding Inventory (PBI), the Mentalization Questionnaire (MZQ), the Brief Symptom Inventory (BSI), and the Borderline Personality Inventory (BPI). Moderated mediation model using PROCESS indicated that the indirect effect of parental attachment security on psychological symptoms severity via mentalizing dimensions was conditional on levels of BPD: parental attachment security via the MZQ-pre-mentalizing modes dimension decreased psychological symptoms in the two groups with higher and medium BPD levels, but not via emotional self-reflection and regulation affect. The findings are discussed in the context of mentalization-based model of BPD, suggesting that hyper mentalizing specifically may play an important role psychological symptoms severity in BPD.