This article presents an analysis of the detrimental effects of relational trauma and multiple facets of loss on infant psychoneurobiology. It examines how the psychotherapeutic treatment of a 3-year old who is mourning the loss of her attachment figure due to abdication of care promotes healthy mourning development and supports the grieving process. There is strong evidence that the child played out painful experiences of loss and vulnerability within the safety of an emotionally attuned therapeutic relationship that served as a secure base and that helped to develop new models of trust. These elements of an attachment relationship in therapy promote Ego development and help to regulate arousal levels and strong emotional reactions.