Abnormalities in hypothalamic–pituitary–adrenal (HPA) axis activity have been reported in patients with psychosis, but it is still unclear how these are related to the clinical symptomatology. Inconsistent findings have emerged from previous studies on the association between cortisol levels and clinical symptoms. Methodological and/or clinical factors, such as patients’ diagnosis or illness phase, might partially account for these inconsistencies. The aim of this study was to investigate the association between HPA axis activity and clinical symptoms in first-episode psychosis, taking into account diagnosis and illness phase.