Background: The child psychiatry unit of the Cochin Hospital in Paris is specialized in a transcultural clinical approach and treatment of psychotraumatism. The clinical demands addressed to the service often combine several levels of vulnerability: recent migration, repeated and intentional traumas, isolation and breach in family bonds sometimes precarious living conditions. Mastering how to approach trauma content adapting to the person’s temporality while taking into account the individual, family and collective dimensions, is a key driver to the clinical intervention (of our approach). Objective and method: We describe a paradigmatic clinical situation articulating its multidimensional complexity: the case of Céline, a 16-year-old Mozambique teenager, unaccompanied minor (UM), who arrived in France three years ago with her 4-year-old child born out of rape. They are both cared for by Paris Child Welfare Bureau. The authors used the CARE guidelines for a rigorous approach to clinical case writing. Results and discussion: In the clinical discussion, we highlight the pertinence of transcultural abilities for the treatment of a complex PTSD (post-traumatic stress disorder). We describe the measures taken to adapt the clinical interview framework to the mother’s psychic temporality, while negotiating what can be said in attendance of the child. The idea of tranquility is primordial—whether she decides to tell or not tell the child. Removing the pressure to have to tell is an element of treatment. Conclusion: Working through a progressive narrative construction, the therapeutical process allowed for the restoration of multiple levels of continuity between times prior to the trauma and following it, as well as prior to migration and following it, to create a continuum from adolescence to adulthood. Restoring narrativity favors the process of becoming a mother and the one of negotiating this new identity. The therapeutic axes also focused on improving the well-being of the UM-mother and preventing the impacts of transgenerational trauma transmission to the child. For women with similar experiences, sharing their emotions and their stories with us makes their choice about telling their child legitimate and comfortable, regardless of the decision they make.