Reliable assessment of daily functioning is essential for guiding rehabilitation in individuals with borderline personality disorder. The 38-item Functional Assessment for Borderline Personality disorder (FAB2) addresses an important gap by simultaneously evaluating the mode of functioning and perceived difficulty. This study examined the FAB2’s properties in a sample of 87 BPD patients and 50 control subjects. The questionnaire showed excellent reliability and robust convergent validity via high correlations with the WHODAS and EMMBEP. Confirmatory factor analysis supported the theoretical structure, establishing the FAB2 as a valid and robust measure for assessing daily functioning in BPD across clinical and research settings.