Dialectical behavior therapy (DBT) is an evidence-based psychotherapy that began with efforts to treat personality disorders and interpersonal conflicts. Evidence suggests that DBT can be useful in treating mood disorders and suicidal ideation, as well as for changing behavioral patterns such as self-harm and substance use. DBT evolved into a process in which the therapist and client work with acceptance and change-oriented strategies, and ultimately balance and synthesize them—comparable to the philosophical dialectical process of thesis and antithesis followed by synthesis.

This approach was developed by Marsha M. Linehan, a psychology researcher at the University of Washington. She defines dialectical as "a synthesis or integration of opposites". DBT was designed to help people increase their emotional and cognitive regulation by learning about the triggers that lead to reactive states and by helping to assess which coping skills to apply in the sequence of events, thoughts, feelings, and behaviors to help avoid undesired reactions.

DBT grew out of a series of failed attempts to apply the standard cognitive behavioral therapy (CBT) protocols of the late 1970s to chronically suicidal clients. Research on its effectiveness in treating other conditions has been fruitful; DBT has been used by practitioners to treat people with depression, drug and alcohol problems, post-traumatic stress disorder (PTSD), traumatic brain injuries (TBI), binge-eating disorder, and mood disorders. Research indicates that DBT might help patients with symptoms and behaviors associated with spectrum mood disorders, including self-injury. Work also suggests its effectiveness with sexual-abuse survivors and chemical dependency.

DBT combines standard cognitive-behavioral techniques for emotion regulation and reality-testing with concepts of distress tolerance, acceptance, and mindful awareness largely derived from contemplative meditative practice. DBT is based upon the biosocial theory of mental illness and is the first therapy that has been experimentally demonstrated to be generally effective in treating borderline personality disorder (BPD). The first randomized clinical trial of DBT showed reduced rates of suicidal gestures, psychiatric hospitalizations, and treatment dropouts when compared to treatment as usual. A meta-analysis found that DBT reached moderate effects in individuals with BPD.