This chapter examines the pivotal role of psychological stress in disease pathogenesis and progression, underscoring the necessity of elucidating the neurobiological mechanisms underlying this phenomenon. The brain is the organ responsible for perceiving, assessing, and managing stress, and its activity is closely linked to the physiological responses that accompany it. Brain-focused psychotherapy represents a promising avenue for influencing the brain structure of both the client and the therapist through interpersonal interactions. These interactions can reinforce existing neural connections, facilitate the formation of new networks, and even induce the generation of new neurons. The process of learning, applying, or recalling information activates the brain, which may result in the formation of long-term memories and potentially new behavioral patterns through neuroplasticity. The term “neuroplasticity” is used to describe the brain’s capacity for change and adaptation. Adult brain cells can reorganize themselves and expand their capacity to process information. This chapter explores the theoretical and practical implications of brain-based psychotherapy for cancer. In general, brain-based psychotherapy can be employed in clinical settings in conjunction with pharmacological interventions for cancer.