The current study investigated whether deficits in mindfulness (the awareness, attention, and acceptance of the present moment) can account for variability in borderline personality (BPD) features and characteristic difficulties in emotion regulation, interpersonal effectiveness, and impulsivity. Structural equation modeling and hierarchical regressions were utilized to examine the associations of trait mindfulness with BPD features, interpersonal problem-solving, impulsive and passive emotion-regulation strategies, and neuroticism in a sample of young adults (N = 342). As hypothesized, mindfulness was related inversely to BPD features and core areas of difficulty, and these associations continued even when controlling for neuroticism. Additionally, mindfulness deficits continued to predict borderline features even when interpersonal effectiveness, passive and impulsive emotion-regulation, and neuroticism were controlled. It is concluded that deficits in mindfulness may be integral to BPD features. Difficulties with attention, awareness, and acceptance of internal and external experience appear to explain borderline pathology even when controlling for problems with negative affectivity, behavioral dyscontrol, and emotional and interpersonal dysfunction--which have been described as definitional of this disorder. Thus, attention to mindfulness deficits may enhance clinical formulation of BPD symptomatology, as well as provide a vital component of effective BPD treatment.