The article presents the importance of validation in the psychotherapy of patients with borderline personality disorder (BPD). The author emphasizes the specific epistemic position in which the psychotherapist, adopting an open, dialectical stance toward multiple perspectives, combines an understanding of the biological and psychosocial factors influencing the patient's functioning with respect for the subjective dimension of their experiences. This is a crucial condition for the effectiveness of validation. Validation is presented as a therapeutic strategy applicable regardless of the psychotherapeutic modality used; it supports the establishment of a therapeutic alliance, facilitates emotion regulation, and creates a relational space that allows reflection and self-discovery. The paper cites experimental research findings indicating a significant effect of invalidation on the level of physiological arousal and on participants’ self-reported negative affect, which further highlights the importance of validation in the therapeutic process. It is also emphasized that the effectiveness of validation ultimately depends on whether the patient truly feels understood and supported by the therapist. In conclusion, the author points to the need for further research into the mechanisms and long-term effectiveness of this strategy in psychotherapy.