In general, research has primarily focused on understanding the psychopathology of borderline personality disorder (BPD), but there has been a paucity of research on processes associated with positive mental health. The present study sought to address this gap in knowledge by investigating associations between daily positive and negative emotions and ego-resiliency and quality of life (QoL) in a clinical sample of 72 women diagnosed with BPD. Using electronic diaries, participants completed end-of-day reports on positive and negative emotions, ego-resiliency, and QoL over a period of 21 days. Multilevel lagged analyses indicated that daily positive emotions were prospectively associated with increased ego-resiliency and QoL the next day, even when adjusting for same-day negative emotions and general psychopathology severity. In addition, the association of daily positive emotions was significantly stronger than the association of negative emotions with both next day ego-resiliency and QoL. Based on these results, we suggest extending the future research agenda to focus more on positive processes associated with ego-resiliency and QoL to achieve a more comprehensive understanding of BPD. We discuss the implications of these findings and argue that symptom reduction alone may not be sufficient. Rather, the research into treatments should be broadened to include testing the effect of interventions on positive emotions and their associations with positive mental health outcomes.