In the scientific literature, no specific link can be established between particular groupings of life events and the development of Borderline Personality Disorder (BPD) in adulthood. A multitude of trajectories can therefore lead to the emergence of the disorder. Given the heterogeneity of manifest events, this article aims to describe childhood relational experiences that may have contributed to the development of borderline pathology. It is proposed that, beyond varying life trajectories and events, these experiences form the latent foundation of the disorder. To support this hypothesis, BPD will first be described from the point of view of symptomatology and personality structure, particularly as regards the use of primitive defensive mechanisms, identity diffusion, alteration of the relation to reality and pathology of object relationships. Then, three types of early relational experiences will be presented and connected with symptomatic and structural characteristics. These experiences refer to failures in the regulation of states of excitation during childhood, excessive experiences of inclusion and exclusion, as well as failures in the parents’ capacity to consider the mental states of the child.