Interpersonal dynamics are a recurring impediment to effective clinical supervision and can lead to phenomena like collusion between the supervisor and supervisee. Collusion involves both supervisor and supervisee engaging in safety behaviours that serve to conveniently avoid and escape from difficult topics and challenging methods. Whilst minimizing the short-term threat to supervisor and supervisee, collusion will tend to undermine the effectiveness of supervision and limit significantly its long-term value to patients. In order to consider how best to address collusion, we review the cognitive-behavioural therapy (CBT) and related literature on collusion, focusing on how it has been formulated and managed. We then provide a case study featuring a supervisor who was colluding with the supervisee's avoidance behaviours (i.e. filling supervision sessions with superficial reflections on his casework) by not challenging these reflections or moving to another learning mode (e.g. experimenting). We develop a CBT formulation of this pattern of supervision as part of the self-reflection process, led by a consultant. Self-reflection appeared to be a useful tool for improving the supervisor's understanding of this dysfunctional process, and strengthened the supervisor's confidence in utilizing relevant skills in the future.