Objectives: This study aims to investigate how childhood trauma and personality traits correlate with the duration of untreated psychosis (DUP). Study Design: A cross-sectional study was conducted over a period of one year. Patients and Methods: The study involves 105 subjects of both genders aged 18 to 45 years, diagnosed with early-course psychosis (less than 5 years duration of illness) and hospitalized at the University Psychiatric Hospital „Sveti Ivan”. The study includes psychotic spectrum diagnoses; from schizophrenia (F20) to unspecified nonorganic psychosis (F29). The main outcome is the defining of DUP as the time period from the appearance of the first psychotic symptom to the start of adequate antipsychotic treatment. Sociodemographic data were collected in a clinical interview, and current psychopathological symptoms were assessed using the PANSS and CGI scales. The respondents provided their own answers to the Childhood Trauma Questionnaire and the Inventory of Personality Organization. Results: The prevalence of childhood trauma in the total sample was 83.8%. The median duration of the DUP was 60.0 days. Neither childhood trauma nor specific personality traits were found to be associated with the DUP. Correlation between certain categories of childhood trauma and personality characteristics was found: violence was associated with more prominent primitive defences, more prominent identity diffusion and more difficulties with reality testing, while other traumatic events were associated with more prominent primitive defences and more difficulties with reality testing. Correlation between current psychopathological symptoms and certain categories of childhood trauma was found: the death of a close person and violence were associated with more prominent positive symptoms; sexual abuse and other traumatic events were associated with less prominent negative symptoms. A correlation was found between more prominent positive symptoms and more difficulties with reality testing. Longer DUP was associated with more prominent positive symptoms and symptoms of general psychopathology. Experiencing death of a close person in childhood, more difficulties with reality testing, and longer DUP predicted more prominent positive symptoms. The experience of another traumatic event in childhood predicted less prominent negative symptoms, while DUP did not contribute to the variance of negative symptoms. Conclusion: Even though no correlation was found between childhood trauma and personality traits and the duration of the DUP, the present study contributes to clarifying the complex interrelationship of the aforementioned constructs, which can be employed in creating more effective and personalized interventions in the treatment of people diagnosed with early-course psychosis.