Emotion dysregulation (ER) is a core symptom of Borderline Personality Disorder. Reducing ER is a main goal of Linehan's Dialectical Behavior Therapy (DBT), adapted for adolescents (DBT-A) by Rathus and Miller (2015). This study investigated two DBT-A modules, Mindfulness and Emotion Regulation, in improving emotion regulation, mindfulness, anxiety, and depression in pre-adolescents ages 9-11. Participants were five pre-adolescents meeting three criteria for Borderline Personality Disorder. Participants, and one parent, completed the DBT-A Mindfulness and Emotion Regulation modules. Hypotheses were generated weekly for pre-adolescent reports of emotion regulation, mindfulness, and diary card emotions of sadness and fear.There was partial support that emotion regulation would improve by end of treatment. Mindfulness showed overall increases by the end of treatment. Self-report decreases in depression scores were clinically meaningful, while parents reported lower, but not clinically meaningful, scores. All parents reported lower anxiety scores, but no clinically meaningful changes, while self-report of anxiety was interpreted with caution because of missing data.