Bulimia nervosa is an eating disorder characterized by binge eating and purging behavior. Previous studies have shown the efficacy of inpatient treatment. With discharge and the associated increased confrontation with everyday stressors as well as the transition to outpatient therapy, there is often a renewed worsening of the symptoms. In order to counteract this development, a smartphone-based aftercare intervention could be a helpful addition to routine outpatient care. We are therefore investigating the efficacy of a four-month, therapist-guided smartphone-based aftercare intervention in a randomized-controlled study using the “Recovery Record” app.