Objective: Psychiatric hospitalized children are considered a high-risk population due to increased internalizing disorders, PTSD diagnosis, and lower cognitive functioning. Furthermore, research with maltreated adolescents within an inpatient psychiatric hospital have demonstrated higher levels of suicidality, violence, and impulsivity compared to those without a history of childhood maltreatment. The current study examined a cumulative model of maltreatment with inpatient children who had been maltreated to understand if maltreatment is related to length of stay in a psychiatric hospital. Method: Children (ages 6–14 years) who had been maltreated and were admitted to a psychiatric children's hospital between 2010–2014 and received a neuropsychological assessment were included in the present study. Results: ANOVAs were conducted and revealed that children exposed to four types of maltreatment had significantly longer hospitalizations stays (M = 33.42 days) compared to those who had been exposed to one type of maltreatment (M = 18.92 days). Furthermore, maltreated children with a diagnosis of PTSD were hospitalized for longer periods of time (M = 28.82 days) compared to maltreated children without a PTSD diagnosis (M = 18.27 days). Regression analyses revealed that working memory partially mediated the relationship between the cumulative effects of maltreatment and length of hospital stay. Conclusion: These findings suggest serious implications for clinicians to understand the importance of the cumulative impacts of maltreatment, working memory, and how these factors may impact psychiatric recovery and symptom reduction.