The mainstay of management of borderline personality disorder is various forms of psychotherapy with medications being found to be of little use.

There has traditionally been skepticism about the psychological treatment of personality disorders, but several specific types of psychotherapy for BPD have developed in recent years. There is growing evidence for the role of psychotherapy in the treatment of people with BPD, with indications that both comprehensive and non-comprehensive psychotherapeutic interventions may have a beneficial effect. Supportive therapy alone may enhance self-esteem and mobilize the existing strengths of individuals with BPD. Specific psychotherapies may involve sessions over several months or, as is particularly common for personality disorders, several years. Psychotherapy can often be conducted either with individuals or with groups. Group therapy can aid the learning and practice of interpersonal skills and self-awareness by individuals with BPD, though drop-out rates may be problematic.

University of Washington psychology professor Marsha Linehan is credited with developing the first empirically supported standard treatment for BPD, termed dialectical behavioral therapy (DBT). DBT grew dramatically in popularity among mental health professionals following the publication of Linehan's treatment manuals for DBT in 1993. DBT was originally developed as an intervention for patients who meet criteria for BPD and particularly those who are highly suicidal.

DBT draws its principles from behavioral science (including cognitive-behavioral techniques), dialectical philosophy and Zen practice. The treatment emphasizes balancing acceptance and change (hence dialectic), with the overall goal of helping patients not just survive but build a life worth living. Treatment is delivered in four stages, with self-harm and other life-threatening issues taking priority. In the second stage, patients are encouraged to experience the painful emotions that they have been avoiding. Stage three addresses problems of living such as career and marital problems. Finally, stage four focuses on helping clients feel complete and reducing feelings of emptiness and boredom.

DBT encompasses four modes of therapy:

The goal of all DBT treatment approaches is to reduce the ineffective action tendencies linked to dysregulated emotions. DBT is based on a biosocial theory of personality functioning in which the core problem is seen as the breakdown of the patient's cognitive, behavioral and emotional regulation systems when experiencing intense emotions. The etiology of BPD is seen as a biological predisposition toward emotional dysregulation combined with a perceived invalidating social environment.

DBT can be based on a biosocial theory of personality functioning in which BPD is seen as a biological disorder of emotional regulation in a social environment experienced as invalidating by the borderline patient.

Several random controlled trials comparing DBT to other forms of cognitive-behavioral treatments have favored the use of DBT to treat borderline patients. Specifically, DBT has been found to significantly reduce self-injury, suicidal behavior, impulsivity, self-rated anger and the use of crisis services among borderline patients. These reductions have been found even when controlling for other treatment factors such as therapist experience, affordability of treatment, gender of therapist and the number of hours spent in individual therapy. In a meta-analysis it was found that DBT was moderately effective. However, none of the studied therapies (including CBT) "fulfilled the criteria for empirically supported treatment." The additional efficacy in the overall treatment of BPD is less clear; future research is needed to isolate the specific components of DBT that are most effective in treating BPD. Furthermore, little research has examined the efficacy of DBT in treating male and minority patients with BPD. Training nurses in the use of DBT has been found to replace a therapeutic pessimism with a more optimistic understanding and outlook.