Because the construct of psychopathy is of chief interest across different disciplines, spanning developmental, clinical, and forensic psychology, its assessment bears far-reaching implications. One prominent contemporary conceptualization of psychopathy, the Triarchic Model, posits that a psychopathic personality encompasses three phenotypic constructs: boldness, meanness, and disinhibition. Recently, triarchic scales have been derived based on items from the Multidimensional Personality Questionnaire (MPQ), and the psychometric characteristics of this approach (MPQ-triarchic [MPQ-Tri]) are promising. The present study examined the longitudinal measurement invariance and the construct validity of the MPQ-Tri scales in a large and diverse high-risk sample (N = 716) across four time points from age 16-25. First, we report and discuss implications of confirmatory and exploratory factor analyses of the MPQ-Tri scales. Next, we report evidence for longitudinal configural and partial scalar invariance. In addition, in line with previous studies, MPQ-Boldness showed relatively higher levels of rank-order and mean-level stability compared to MPQ-Meanness and Disinhibition. Finally, in terms of construct validity, the MPQ-Tri scales showed a pattern of association with external correlates across internalizing and externalizing domains that were largely in line with theoretical expectations. One partial exception concerned the limited discriminant validity of the MPQ-Meanness and Disinhibition scales. On balance, the present findings suggest that the MPQ-Tri scales fulfill their intended purpose, with some noted limitation, and provide grounds for the use of the MPQ-Tri scales in developmentally-informed studies on the etiology and consequences of psychopathy. (PsycInfo Database Record (c) 2021 APA, all rights reserved).