The aim of this paper is to briefly present the current knowledge on the definition of relational trauma, place in classifications, prevalence, consequences, and applied therapeutic methods. Reports from many countries indicate that in the relationship with adults, usually parents, on whom the child is dependent for many years, various forms of abuse may occur, related not only to violence, but also to emotional, physical, and intellectual neglect. Behind them, the unregistered area of aversive experiences of children who enter adulthood with the experience of relational trauma is hidden. These adverse childhood experiences significantly affect overall functioning in adulthood. For years, researchers of the phenomenon have been paying attention to the existence of a separate diagnosis related to relational trauma. The 11th edition of the International Classification of Diseases (ICD-11) introduces a new diagnosis: complex post-traumatic stress disorder (Complex PTSD, cPTSD). New methods of therapeutic interventions emerge, and the validation of these methods and explanation of the mechanisms of action is research work for the coming years.