Patients with psychosis have higher rates of childhood trauma, which is also associated with adverse effects on cognitive functions such as attention, concentration and mental speed, language, and verbal intelligence. Although the pathophysiological substrate for this association remains unclear, these cognitive deficits may represent the functional correlate of changes observed in relation to trauma exposure in structures such as the amygdala and the hippocampus. Interestingly, these structures are often reported as altered in psychosis. This study investigated the association between childhood trauma, cognitive function and amygdala and hippocampus volume, in first-episode psychosis. We investigated 83 patients with first-episode psychosis and 63 healthy controls. All participants underwent an MRI scan acquired with a GE Sigma 1.5-T system, and a standardized neuropsychological assessment of general cognition, memory, processing speed, executive function, visuo-spatial abilities, verbal intelligence, and language. In a subsample of the patients (N=45) information on childhood trauma was collected with the Childhood Experience of Care and Abuse Questionnaire (CECA.Q). We found that amygdala, but not hippocampus, volume was significantly smaller (p=0.001) in patients compared to healthy controls. There was a trend level interaction for hippocampus volume between group and sex (p=0.056). A history of childhood trauma was associated with both worse cognitive performance and smaller amygdala volume. This smaller amygdala appeared to mediate the relationship between childhood trauma and performance on executive function, language and verbal intelligence in patients with psychosis. This points to a complex relationship between childhood trauma exposure, cognitive function and amygdala volume in first-episode psychosis.