Objective: A general lack of supervision outcome studies and new advancements within therapist training methods inspired us to develop a randomised controlled trial, Case formulation and ALLiance (CALL), testing the efficacy of a brief pre-treatment training session. CALL combines generic case formulation and alliance principles with the supervision of a specific client. This qualitative study acts as a preliminary to the randomised controlled trial and aims to explore psychologists' experiences of participating in CALL. Method: Semi-structured interviews were conducted with seven psychologists in private practice, who participated in CALL between January and May 2020. The transcribed interviews were analysed using thematic analysis. Results: The psychologists described CALL as a clinically useful and collegial experience but simultaneously conveyed a lack of recollection of the training session and doubts as to its enduring utilisation. Conclusion: CALL has the potential to positively influence the process and outcome of therapy through the fostering of case formulation and alliance management skills, as well as a strong supervisory alliance. However, the familiar content or brief format of the session, and participants' memory bias, may have limited the utilisation and recall of the intervention.