Abstract We used a daily process design and multilevel modeling to examine the role of borderline personality features in the day-to-day stability of college students' negative affect and self-esteem and their reactivity to interpersonal stressors. At the end of each day for two weeks, students completed a checklist of daily stressors and measures of state affect and self-esteem. We predicted that high scores on a measure of borderline features would be related to more daily interpersonal stressors, greater negative affective and self-esteem reactivity to these stressors, and less day-to-day carryover of negative mood and self-esteem. The first and third hypotheses were supported, but not the second. The findings demonstrate the utility of a daily process methodology and multilevel modeling to study the day-to-day functioning of individuals with borderline features.