Criminal legal system-involved populations are disproportionally impacted by chronic health conditions relative to the general population. These discrepancies are thought to be due to both health disparities and increased likelihood to engage in health-compromising behaviors. Medical conditions can significantly influence neuropsychological functioning and, in turn, thinking and behavior relevant to clinical forensic decision-making and psychological practice in criminal legal settings. The aim of this article is to review medical conditions commonly observed among system-involved populations-specifically cardiovascular disease, human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), traumatic brain injury, cancer, diabetes, and medication side effects-and describe the complex and important links between these conditions, their associated neuropsychological deficits, and applications to psychological assessment and treatment in criminal legal settings. Ultimately, this discussion will be useful to staff providing psychological services in these settings by increasing their familiarity with these concepts, and providing practical applications to inform their case conceptualization, assessment, and treatment services with system-involved individuals. (PsycInfo Database Record (c) 2022 APA, all rights reserved).