Background: A common aspect of evidence-based treatments for people with borderline personality disorder (BPD) is pedagogical interventions and formats. In mentalization-based treatment (MBT) the introductory course has a clear pedagogical format, but a pedagogical stance is not otherwise defined. Methods: Treatment integrity was quantitatively assessed in a sample of 346 individual MBT sessions. Nine group sessions and 24 individual MBT sessions were qualitatively subjected to interpretative phenomenological analysis (IPA). Results: The dominating intervention type was MBT Item 16therapist checking own understanding (31% of the interventions). IPA unveiled the following: (1) a pervasive, but hidden/ implicit psychopedagogical agenda, (2) psychopedagogical content seemed precious for the patients, and (3) four tentative strategies for pedagogical interventions in MBT (a) independent reasoning; (b) epistemic trust; (c) mental flexibility; and (d) application of verified insights, knowledge, or strategies. Conclusion: Development and clarification of the pedagogical stance in MBT could further improve the quality of therapists' interventions.