Background: Depersonalization occurs in healthy individuals and across a broad range of psychiatric patients. Data on depersonalization in persons linked to patients through genetics, environment or education are scarce. Due to their higher risk of developing psychosis, first-degree healthy relatives might show differences with the general population. This study examines depersonalization in patients with schizophrenia or schizophrenia spectrum disorders, their first-degree healthy relatives and normal controls. Methods: The Cambridge Depersonalization Scale was used to measure depersonalization in a sample of 147 clinically stable patients with schizophrenia or schizophrenia spectrum disorders, 73 first-degree relatives with no psychiatric history and 172 healthy controls. Mixed effect models were used to account for both the familial structure of the data and the effect of sociodemographic characteristics. Results: Patients obtained higher scores than relatives and controls for frequency and duration of depersonalization experiences, number of items responded positively and total depersonalization, while first-degree relatives obtained lower scores than patients and controls for all these characteristics. Conclusions: First-degree relatives of patients reported fewer episodes of depersonalization, which were less intense and of shorter duration, than healthy controls. This finding might be related to a protection mechanism that keeps first-degree relatives away from near-psychotic experiences. The nature of such a mechanism remains to be discovered.