Mentalization based therapy (MBT) has developed its therapeutic stance and interventions based on attachment theory. Accordingly, prescribed MBT interventions are likely to resemble the way securely attached therapists speak in sessions. This paper will compare the Therapists Attunement Scales (TASc)-an instrument that assesses therapist attachment classification based on how therapists speak during a single session-to MBT interventions in two ways. First, by a conceptual comparison of the linguistic markers from the TASc with the prescribed MBT interventions. Second, by analyzing a therapy session of an expert MBT clinician with the TASc. Our comparison shows that the interventions of adherent MBT therapists are very similar to the language of secure therapists. Conversely, the communicative style of therapists with an insecure attachment classification does not align well with quality MBT interventions and is not conducive to the development of epistemic trust. Adherent MBT is likely to reflect the therapist's personal attachment classification and associated communicative style, and insecure attachment styles are likely to be an obstacle to acquiring competences in MBT. Implications for training and future research are discussed.