The current study evaluated the relative associations of the DSM-5 Section II operationalization of Borderline Personality Disorder (BPD) and dimensional traits included in a diagnosis of BPD in DSM-5 Section III with conceptually relevant external criterion variables. It is important to determine whether or not Section II BPD and constellation of Section III BPD traits have similar positions in the nomological network representing the BPD construct. Moreover, it is important to determine whether or not the trait-based Section III BPD diagnosis is an improvement upon the categorical Section II diagnosis in regard to its associations with external criteria. To evaluate this, we used two samples, a patient sample consisting of 145 psychiatric patients and a university sample consisting of 399 undergraduate students. We conducted a series of correlation and regression analyses in order to determine the relative associations of these two diagnostic methodologies with relevant external criteria. Correlation analyses did not favor either model, but indicated that both Section II and Section III BPD have associations with external criterion variables relevant to BPD. The regression analyses tended to favor the trait-based Section III model, supporting the construct validity and use of the trait profile for BPD in DSM-5 Section III. Generally, it was concluded that the Section II and Section III operationalizations have similar positions in a nomological network representing the BPD construct.