This scoping review critically assessed evidence regarding mental disorders among mothers involved with the criminal justice system (CJS) and provided pooled prevalence rates of mental disorders. In total, 27 studies were included in the review, with 23 studies from the United States of America and 26 focused on incarcerated mothers. The findings supported the evidence on substantial burden of mental disorders, among CJS-involved mothers. Several factors contributing to mental disorders were identified, including history of abuse/incarceration/mental illness, a greater number of pregnancies, child-rearing responsibilities, less contact with children, and poor social support, which were organised using a socioecological model. However, significant gaps in the current evidence base were apparent, including inconsistencies in methodologies and outcomes assessed and a lack of large, longitudinal studies. The study highlights the importance of high-quality longitudinal research to extend knowledge around causal pathways between different risk or protective factors and mental disorders among CJS-involved mothers.