Treatment dropout among individuals with borderline personality disorder (BPD) is associated with negative psychosocial outcomes. Identifying predictors of dropout among this population is critical to understanding how to improve treatment retention. The present study extends the current literature by examining both static and dynamic predictors of dropout. Chronically suicidal outpatients diagnosed with BPD (N = 42) were randomly assigned to a 20-week dialectical behavior therapy (DBT) skills training group. Static and dynamic predictors were assessed at baseline, 5, 10, 15, 20 weeks, and 3 months post-intervention. A post-hoc two-stage logistic regression analysis was conducted to predict dropout propensity. Receiving disability benefits at baseline and decreases in mindfulness were associated with significantly increased probability of dropout. Clinicians working with chronically self-harming outpatients diagnosed with BPD would benefit from prioritizing clinical interventions that enhance mindfulness in order to decrease dropout propensity.