Recently, theorists have posited the development of epistemic trust -the trust in others as reliable sources of information -as an essential aspect of the therapeutic relationship and a mechanism of therapeutic change. Epistemic trust is likely to be disrupted in adoptive children and families and Mentalization Based Treatment (MBT) aims to explicitly promote its development. Therefore, this study aims to investigate how epistemic mistrust is addressed and how epistemic trust is established within the MBT framework. This single-case, exploratory study reports data from in-depth interviews with one adoptive family, which were analyzed qualitatively using Interpretative Phenomenological Analysis. Two superordinate themes are reported: pre-therapy factors contributing to epistemic mistrust and factors contributing to the development of epistemic trust. The findings highlight two critical elements in establishing epistemic trust: the use of certain clinical skills that help build a secure base within therapy and the possibility of trust being transferred from and to other professionals/systems beyond therapy. Hence, this study informs a deeper understanding of how epistemic trust may be built in therapeutic work with adopted children and identifies possible clinical approaches that may be used by clinicians working with this client group.