Background: Child maltreatment has been associated with a wide range of mental disorders in adulthood. Whether child maltreatment is specifically associated with psychosis risk in individuals at ultra-high risk (UHR) for psychosis, or leads to a general vulnerability for overall psychopathology in the UHR stage remains unclear. The present study examines the association between child maltreatment and transition to psychosis and other mental disorders. Methods: The sample consisted of 259 UHR individuals from the EUropean network of national schizophrenia networks studying Gene-Environment Interactions (EU-GEI) study. Participants were followed-up for 2 years to assess clinical outcome. Clinical outcome was assessed at 6 months, 12 months, and 24 months after baseline. Child maltreatment before the age of 17 years was assessed at baseline. Results: Our findings show that a history of emotional abuse was associated with an increased risk for transition to psychosis (OR = 3.78, 95% CI = 1.17 to 12.39, P = -027). Apart from psychosis, a history of physical abuse was associated with depressive disorder (OR = 4.92, 95% CI = 2.12 to 11.39, P = .001), post-traumatic stress disorder (OR = 2.06, 95% CI = 1.10 to 3.86, P = .023), panic disorder (OR = 2.00, 95% CI = 1.00 to 3.99, P = .048) and social phobia (OR = 2.47, 95% CI = 1.18 to 5.16, P = .016) at follow-up. Conclusion: Our findings suggest that in the UHR stage child maltreatment is a pluripotent risk factor for developing psychosis, depressive disorder, post-traumatic stress disorder (PTSD), panic disorder, and social phobia in adulthood.