This exploratory study investigated the extent to which clinicians (N = 13) differed in their causal conceptualisation of Major Depressive Disorder (MDD), and if systematic differences could be attributed to clinician characteristics. Therapist effects, individual clinician characteristics that systematically impact treatment outcomes, have been extensively studied but the impact clinician characteristics have on other stages of the therapeutic trajectory is relatively unknown. Clinician beliefs appear to impact diagnostics, proposed interventions, and differences in individual case conceptualisations. Clinician characteristics such as theoretical orientation, and associated beliefs surrounding disorder aetiology and intervention, may also influence how clinicians conceptualise disorders. While symptoms are presented a-causally in diagnostic manuals, clinicians have been shown to reason about them causally. Perceived Causal Networks (PECANs) systematically capture subjective causal relationships and were used to visualise and analyse clinicians’ conceptualisations. Individual PECANs revealed differences in the causal conceptualisation of MDD, as did PECANs aggregated based on clinicians’ aetiological beliefs about MDD. These differences in conceptualisation may influence clinicians’ decisions and behaviour during the therapeutic trajectory and reflect patients’ differing therapeutic experiences.