Importance: Childhood adversity has been linked to many indicators of shorter healthy lifespan, including earlier onset of disease and disability as well as early mortality. These observations suggest the hypothesis that childhood maltreatment may accelerate aging. We tested this hypothesis in a prospective cohort of individuals with documented childhood maltreatment and controls matched on demographic and socioeconomic factors. Objective: To characterize the relationship between childhood maltreatment and accelerated biological aging in a prospective cohort of documented cases of childhood maltreatment and matched controls.Design: Prospective cohort study Setting: Cases were drawn from juvenile and adult court records from the years 1967 through 1971 in a large Midwest metropolitan geographic area. Controls were selected from the same schools and hospitals of birth and matched on age, sex, race, and approximate socioeconomic status. Participants: 357 individuals with documented cases of childhood maltreatment and 250 matched controlsExposure: Court-substantiated cases of childhood physical or sexual abuse, or neglect occurring at age 11 or youngerOutcome: Biological aging quantified using two blood-chemistry algorithms, the Klemera-Doubal method Biological Age (KDM BA) and the PhenoAge, developed and validated in data from the National Health and Nutrition Examination Surveys (NHANES) using published methods and publicly available software. Results: Participants (55% women, 49% non-White) had mean age of 41 years (SD=4). Those with court substantiated childhood maltreatment history exhibited more advanced biological aging as compared with matched controls, although this difference was statistically different for only the KDM BA measure (KDM BA Cohen’s D=0.20, 95% CI=[0.03,0.36], p=0.02; PhenoAge Cohen’s D=0.09 95% CI=[-0.08,0.25], p=0.296). In subgroup analyses, maltreatment effect sizes were larger for women as compared to men and for White participants as compared to non-White participants, although these differences were not statistically significant at the α=0.05 level.Conclusions and Relevance: As of midlife, effects of childhood maltreatment on biological aging are small in magnitude but discernible. Interventions to treat psychological and behavioral sequelae of exposure to childhood maltreatment, including in midlife adults, have potential to protect survivors from excess burden of disease, disability, and mortality in later life.