Aim: To investigate the relationship between anomalous self-experiences and duration of untreated psychosis in a sample of patients with first-episode schizophrenia spectrum disorders. Methods: Anomalous self-experiences were assessed by means of the Examination of Anomalous Self-Experience manual in 55 patients referred to their first adequate treatment for schizophrenia. Diagnoses, symptom severity, functioning and childhood trauma were assessed using the Structured Clinical Interview for the Positive and Negative Syndrome Scale, Premorbid Adjustment Scale, Social Functioning Scale and Childhood Trauma Questionnaire. Substance misuse was measured with the Drug Use Disorder Identification Test, and alcohol use was measured with the Alcohol Use Disorder Identification Test. Duration of untreated psychosis was measured in accordance with a standardized procedure. Results: High levels of anomalous self-experiences are significantly associated with longer duration of untreated psychosis, an association which held after correcting for other variables associated with long duration of untreated psychosis. Conclusions: The field of early detection in psychosis is in need of additional clinical perspectives to make further progress. Improved understanding and assessment of anomalous self-experiences may help clinicians to detect these important phenomena and provide earlier help, and thus reduce treatment delay.