Findings suggest that the way an individual understands their experiences has important consequences on subsequent health behaviour. One aspect of an individual's understanding is what they believe has caused their experiences. This has been associated with treatment outcome and attitudes towards mental health problems. The aim of this systematic review was to examine the impact of causal beliefs on treatment outcome and stigma in people experiencing psychosis. Three main databases were searched and 21 articles that investigated various aspects of treatment outcome, and stigma in relation to causal beliefs was included in the review. Overall, there were a small number of replicated findings which limits the interpretation of results. There is an indication that causal explanations are associated with various treatment outcomes, including attitudes towards treatment and satisfaction with therapeutic relationships as well as internalized stigma. Spiritual beliefs appeared to be adopted as a coping mechanism and a way to reduce stigma but did not appear to be associated with treatment outcome. Individuals with psychosis do appear to develop causal beliefs that may be associated with engagement with services and treatment, as well as impacting on their attitudes towards themselves and others with mental illness. This may have important implications for clinical practice. Copyright © 2016 John Wiley & Sons, Ltd. Key Practitioner Message Individuals who have experience of psychosis develop their own subjective causal explanations, and these can be complex and contradictory. An individual's causal explanation may influence how they engage with services and treatment, as well as providing a way of coming to terms with their difficulties. Causal explanations may also contribute to the experience of stigma, which is often a significant barrier to recovery for this client group.