The prevalence of childhood trauma (CT) in schizophrenia spectrum disorders (SSDs) and substance abuse disorders (SUDs) is high. Direct comparisons of CT in these disorders are lacking, and it is not known whether there are differences in self-reported CT in SSDs as compared to SUDs. We aimed to compare the frequency, severity and types of CT in SDDs and SUDs. Patients with SSDs (n = 57) and SUDs (n = 57) were matched for age and gender. Overall levels of CT and CT subtypes were measured retrospectively by the Childhood Trauma Questionnaire Short-Form (CTQ-SF), and grouped into none/low and moderate/severe levels of CT. Group differences in CTQ-SF sum score and subscale scores, as well as differences in the severity of overall CT and CT subtypes were all non-significant. In both groups, 64.9% reported ≥ 1 subtypes of CT above cut-off. Of those who reported CT above the cut-off, 13.5% in the psychosis group reported ≥ 4 subtypes, as compared to 2.7% in the substance abuse group. We did not find statistically significant differences between SSDs and SUDs in terms of exposure to CT frequency or severity, all effect sizes were small (r < 0.15).