Children with autism spectrum disorder (ASD) with and without co-occurring schizophrenia spectrum traits (SST) were examined for differences in co-occurring psychiatric symptoms, background characteristics, and mental health risk factors. Participating mothers and teachers completed a DSM-IV-referenced rating scale and a background questionnaire (mothers only) describing 147 children (6–12 years) with ASD. There was a clear pattern of group differences in co-occurring psychiatric symptom severity (+SST > SST−) and background characteristics. Children with impairing SST had more mental health risk factors. Girls were more likely to be classified SST according to mothers’ ratings. Children born in spring–summer were more likely to be classified non-SST by teachers’ ratings. Findings provide tentative evidence that SST may be a useful marker of behavioral heterogeneity within the ASD clinical phenotype.