The alternative model of personality disorders (AMPD) traits were designed to maintain continuity with the Section II personality disorder (PD) diagnoses by retaining the same clinical information. Whether the AMPD traits achieve this is not well established. Prior work testing incremental validity of AMPD traits and Section II diagnoses is limited by the fact each model was measured by a different instrument or rater, making it unclear whether discrepancies are due to the constructs or methods. Here, we compare the incremental validity of AMPD traits versus Section II PDs assessed by the same instrument and rater. Participants (N = 311, 50% received past-year mental health treatment) completed a clinical interview, baseline self-reports, and 14-day ambulatory assessment protocol. Interviewers rated AMPD domains, facets, and Section II criteria from the same interview (Structured Interview for DSM-IV Personality). We used hierarchical regression models to evaluate the variance predicted in 17 clinically relevant cross-sectional and momentary variables by the AMPD traits and Section II PDs. Incremental R² showed that Section II PDs account for little variance in outcomes over and above the AMPD domains/facets, whereas the AMPD facets were generally more predictive of outcomes than the Section II PDs. Results add novel evidence that dimensional PD traits-not a particular assessment method-are equivalent or superior to PD categories for predicting social, emotional, and behavioral functioning. (PsycInfo Database Record (c) 2024 APA, all rights reserved).