Historically, many cases of demonic possession have masked major psychiatric disorder. Our aim is to increase awareness that symptoms of schizophrenia are still being classified as demonic possession by priests today. We report the case of a 28-year-old patient who had been diagnosed 5 years previously with paranoid schizophrenia (treated with clozapine, risperidone, ziprasidone and onlanzapine without a complete response) and was also receiving treatment in a first episode psychosis unit in Spain. The patient was led to believe by priests that her psychotic symptoms were due to the presence of a demon. This was surprising because some of the priests were from the Madrid archdiocese and knew the clinical situation of the patient; however, they believed that she was suffering from demonic possession, and she underwent multiple exorcisms, disrupting response to clinical treatment. Patient insight is an important factor in response to treatment, so religious professionals should encourage appropriate psychiatric treatment and learn about mental illnesses.