Objective. To design a questionnaire to assess cognitive representations of mental health problems held by people diagnosed with schizophrenia. Background. Personal beliefs about health problems have been reliably associated with emotional and behavioural responses to those health problems and health outcomes. This area has been extensively explored in relation to physical health, but somewhat neglected in mental health. In this study, a questionnaire designed to assess key beliefs about physical illness (the Illness Perception Questionnaire–Revised) was modified for use in exploring beliefs about schizophrenia. The new measure was termed the Illness Perception Questionnaire for Schizophrenia (IPQS). Method. Participants were 124 people with a diagnosis of schizophrenia who completed the IPQS and additional measures to assess symptom severity, emotional state, and attitudes towards medication. The psychometric properties of the IPQS were analysed, including internal consistency, test–retest reliability, and discriminant and concurrent validity. Results. The IPQS subscales were shown to be internally reliable, and reliable over time. Correlations with measures of symptom severity, emotional state, and attitudes towards adherence to medication showed that the subscales were measuring the constructs that they were designed to measure. Conclusions. The IPQS is a reliable and valid measure of cognitive representations of mental health problems held by people with a diagnosis of schizophrenia.