Currently recommended psychotherapies for depression are not always delivered in a consistent manner. There is an assumption that the use of clinical supervision will ensure reliable treatment and patient recovery. However, there is limited research supporting this assumption. This study explored the role of supervision in the treatment of depression. In particular, it examined how supervisors’ own characteristics and those of patients can influence the focus of supervision sessions. Clinical supervisors who worked with cognitive behavioural therapy (CBT) therapists treating depression cases were asked to indicate their supervision focus for three different patient vignettes. These vignettes varied in clinical complexity. Participants’ intolerance to uncertainty and their self-esteem were also assessed. Supervisors tended to focus their supervisees on the use of evidence-based therapeutic techniques for both straightforward and complex cases. However, their approach was less evidence-based for diffuse cases. Three supervisory types emerged: an ‘Alliance- and Technique-Focused’ group, a ‘Case Management-Focused’ group, and an ‘Unfocused’ group. Personal characteristics of the supervisors varied across the groups. The content of supervision sessions is influenced by factors from outside the therapy process. These factors might cause supervisors to avoid focusing on evidence-based aspects of therapy, thus feeding therapist drift. Suggestions are made for new supervision protocols that consider the supervisor's personal characteristics.