Borderline personality disorder (BPD) and depression are characterized by negative emotionality, yet BPD is also theorized to be linked with emotional variability. The present study extends past work to a larger time scale and notes the degree to which stress-related emotional responses are variable or persistent across stressors using novel analytic models. Participants ( = 164) were undergraduate students who completed daily assessments of negative emotional responses to interpersonal stressors for 2 weeks. BPD and depression were associated with greater negative emotional intensity and greater emotional variability in response to nonsocial stressors. Only BPD features were associated with greater emotional variability in response to social stressors. This study is limited by its reliance on self-report in a nonclinical sample and limited within-person assessments. Data point to distinct constellations of emotional dysfunction in BPD and depression. Pending replication, these data may inform targeting of emotional dysfunction in treatment.