Although emotion dysregulation has consistently been conceptualized as a core problem of borderline personality disorder (BPD), a comprehensive, and empirically and ecologically validated model that captures the exact types of dysregulation remains absent. In the present article, we combine insights from basic affective science and the biosocial theory of BPD to present a theoretical model that captures the most fundamental affective dynamical processes that underlie BPD and stipulates that individuals with BPD are characterized by more negative affective homebases, higher levels of affective variability, and lower levels of attractor strength or return to baseline. Next, we empirically validate this proposal by statistically modeling data from three electronic diary studies on emotional responses to personally relevant stimuli in personally relevant environments that were collected both from patients with BPD (N = 50, 42, and 43) and from healthy subjects (N = 50, 24, and 28). The results regarding negative affective homebases and heightened affective variabilities consistently confirmed our hypotheses across all three datasets. The findings regarding attractor strengths (i.e., return to baseline) were less consistent and of smaller magnitude. The transdiagnostic nature of our approach may help to elucidate the common and distinctive mechanisms that underlie several different disorders that are characterized by affective dysregulation.