The factor structure of the Brief Symptom Inventory--18 (BSI-18; L. R. Derogatis, 2000) was investigated in a sample of adult survivors of childhood cancer enrolled in the Childhood Cancer Survivor Study (CCSS; N = 8,945). An exploratory factor analysis with a randomly chosen subsample supported a 3-factor structure closely corresponding to the 3 BSI-18 subscales: Depression, Anxiety, and Somatization. Confirmatory factor analysis with structural equation modeling validated this 3-dimensional structure in a separate subsample, though an alternative 4-factor model also fit the data. Analysis of the 3-factor model showed consistent fit in male and female participants. Compared with available community-based norms, survivors reported fewer symptoms of psychological distress. Together, results support the hypothesized 3-dimensional structure of the BSI-18 and indicate the measure may be useful in assessing psychological distress in this growing population of cancer survivors.