Borderline personality disorder (BPD) has been associated with a reduced functional flexibility of the autonomic nervous system (ANS), indexed by decreased vagally mediated heart rate variability (vmHRV). Employing a comprehensive Section II-based assessment approach and a partial Section III-based assessment approach (including Criterion A of the alternative model of personality disorders [AMPD]), the present study investigates how different conceptualizations of personality disorders (PDs) according to the Diagnostic and Statistical Manual for Mental Disorders, 5th edition relate to ANS function. Using the BPD section of the Structured Clinical Interview for DSM-IV Axis II Disorders (SCID-II, a Section II-based assessment approach) and the Semistructured Interview for Personality Functioning DSM-5 (STiP-5.1, a Section III-based assessment approach), we conducted linear regression analyses to examine how categorical (BPD diagnosis) and dimensional (severity and domain) measures of PD are associated with ANS activity among adolescent psychiatric patients (N = 147, Mage = 15.25 years). Replicating earlier findings, analyses revealed a statistically significant positive association between the SCID-II measures of BPD and heart rate (HR), b = 0.43, t(59) = 3.57, p = .001, f = .57, as well as a statistically significant negative association between the SCID-II measures of BPD and vmHRV, b = -0.34, t(59) = -2.74, p = .008, f = .47. Neither the STiP-5.1 total score nor the subscales of the Level of Personality Functioning Scale (LPFS) were associated with HR or vmHRV. The present findings indicate that the SCID-II may capture features of PD that are more informative of variance in physiological function than the STiP-5.1. (PsycInfo Database Record (c) 2023 APA, all rights reserved).