Mental health practitioners' beliefs about the causes of mental illness may influence their approach to treatment and impact therapeutic outcomes. There has been limited research on this topic. This study explores mental health practitioners' views and experiences of addressing causal beliefs in treatment. A thematic framework guided the analysis of semi-structured interviews with 17 mental health practitioners. Participants stated that their causal beliefs impact their approach to treatment, and clients' causal beliefs influence how clients approach treatment. Participants thought that it was important to discuss causes with clients and identified several barriers to, and consequences of, doing so. Participants identified that addressing causal beliefs in treatment influenced factors such as practitioner empathy, therapeutic alliance, engagement in treatment and clients' self-blame.