The deleterious effects of sexual abuse (SA) are well documented, as many studies have found that SA can increase the risk for psychiatric disorders. While SA has been examined in multiple samples, no studies have examined the characteristics of SA in individuals with severe mental illnesses (SMI). This study examined the prevalence rate and characterized the nature of SA among individuals with SMI who were under psychiatric care in three different inpatient facilities. Utilizing data from the MacArthur Violence Risk Assessment Study, 1,136 individuals with SMI were assessed for SA histories, psychiatric diagnoses, and other demographics. Nearly half of this sample (n = 511) identified SA histories, with almost half indicating that the person was a stranger or someone outside of the family unit. One third reported SA occurred "too many times to count," and approximately a third indicated the abuse consisted of intercourse, occurring at a mean age of 11.22 years. Results found that individuals with SA histories were often never married, Caucasian, female, had children, described themselves as psychologically unwell, and were commonly voluntary psychiatric admissions. Those with SA histories had significantly higher psychopathology and lower functioning, and were more likely to be diagnosed with depression but less likely to be substance dependent. Identifying SA characteristics in individuals with SMI is a critical component to successful treatment. Thorough screening and assessment of this common problem can help clinicians identify accompanying issues that may exacerbate SMI symptomology, and improve the prognosis for long-term outcomes.