The concept of an ‘internal supervisor’ has been used in psychotherapy to describe the way in which the supervisory relationship is internalized and utilized by the supervisee. This research explores the possibility, and potential benefit, of training therapists to develop a ‘compassionate internal supervisor’. A training programme was developed for trainee cognitive‐behavioural therapists using adapted versions of compassion‐focused therapy interventions. The training focused on guided imagery exercises and reflective practices undertaken for a 4‐week period. Seven trainee cognitive‐behavioural therapists were interviewed, utilizing a semi‐structured format, regarding their experience of the training programme. The resulting transcriptions were analysed using Interpretative Phenomenological Analysis (IPA). The analysis identified six super‐ordinate themes: (1) the varied nature of the supervisor image, (2) blocks and their overcoming, (3) increased compassion and regulation of emotion, (4) impact on cognitive processes, (5) internalization and integration, and (6) professional and personal benefit. The themes describe the varied ways in which participants created and experienced their compassionate supervisor imagery. Working with the personal blocks encountered in the process provided participants with a deeper understanding of the nature of compassion and its potential to support them in their training, practice and personal lives. The process and impact of ‘internalizing’ a compassionate supervisory relationship is described by participants and then discussed for potential implications for psychotherapy training and self‐practice. Copyright © 2016 John Wiley & Sons, Ltd. Key Practitioner Message Compassion‐focused therapy, and related compassionate‐mind imagery exercises, can be adapted specifically to develop compassion in trainee psychotherapists. Creating, and engaging with, an ’ideal compassionate supervisor‘ in an imaginal form can support psychotherapy trainees in their clinical practice and development, their supervision and their personal lives. The cultivation of therapist self‐compassion can reduce unhelpful cognitive processes such as worry, rumination and self‐criticism whilst increasing self‐reflection, attentional flexibility and approach behaviour. Identifying, and working with, blocks to compassion is important when cultivating clinician self‐compassion Therapist self‐practice of compassion‐focused exercises can provide important insights into the nature of compassion and its cultivation in clients