Emotion dysregulation is a core feature of borderline personality disorder (BPD). However, there is a dearth of literature examining the association between the dysregulation of positive emotions and BPD. The present study assesses the reciprocal and longitudinal associations between positive emotion dysregulation and BPD features. Participants were 149 community women currently experiencing intimate partner violence and using substances (Mage = 40.3, 30.8% Black). BPD was assessed at baseline via a clinician-administered diagnostic interview. Participants self-reported on positive emotion dysregulation and BPD features at baseline and 1-month follow-up sessions. Positive emotion dysregulation did not significantly predict BPD features at 1-month follow-up when controlling for initial BPD features (β = -.09, SE = 0.07, p = .21, confidence interval [CI] [-0.23, 0.10]). However, BPD features did significantly predict positive emotion dysregulation at 1-month follow-up, when controlling for initial positive emotion dysregulation (β = .25, SE = 0.10, p = .01, CI [0.07, 0.44]). This study offers initial insight into the nature of the association between BPD and positive emotion dysregulation over time among women experiencing intimate partner violence and using substances. Findings highlight the role of BPD features in the exacerbation of positive emotion dysregulation, which may inform targeted assessments and treatments in this area. (PsycInfo Database Record (c) 2024 APA, all rights reserved).