Behavioral activation is an effective treatment for depression, based on targeting deprivation of positive rewards. It becomes more and more evident that many forms of mental disorders and psychological suffering involve reduction of goal-driven and pleasant activities. This reduction leaves negative mental states free to take the center of consciousness, without being counterbalanced by positive feelings, memories, and experiences of agency, self-efficacy, competence, relaxation, energy, and satisfaction. Reduced activity can be found in disorders ranging from chronic pain to personality disorders and schizophrenia. We believed that the time was ripe to reason that behavioral activation, more than a treatment in itself, can be considered a fundamental mechanism of change in the psychotherapy for a wide range of dysfunctions, irrespective of the clinician’s preferred orientation. In this special section, authors from diverse orientations describe how they integrate behavioral activation in their clinical practice, while providing rich and detailed clinical illustrations. We reflect that behavioral activation needs to be implemented in many forms of psychotherapy and for a wide range of disorders. Moreover, it has the potential to make treatment faster and maximize outcomes, as long as it is delivered under careful consideration of the therapy relationship.