Background and Objective: Maternal mental disorders are implicated in a range of adverse perinatal outcomes, although few studies have examined these links among Australian Aboriginal populations. We aimed to evaluate the association between maternal mental disorders and key adverse perinatal outcomes among Aboriginal neonates. Methods: We used whole population-based linked data to conduct a retrospective cohort study (N=38,592) using all Western Australia singleton Aboriginal births (1990–2015). Maternal mental disorders were identified based on the International Classification of Diseases codes and grouped into six broad diagnostic categories (severe mental disorder, common mental disorder, personality disorder, substance use disorder, and all other adulthood- and childhood-onset mental disorders). Perinatal outcomes evaluated included preterm birth, small for gestational age, perinatal death, major birth defect, fetal distress, low birth weight, and low Apgar score. We employed log-binomial/-Poisson models to calculate risk ratios (RRs) and 95% confidence intervals (CIs). Results: After adjustment for sociodemographic factors and pre-existing medical conditions, having a maternal mental disorder (within the five years prior to birth) was associated with adverse perinatal outcomes, with RRs (95% CIs) ranging from 1.26 (1.17, 1.36) for fetal distress to 2.00 (1.87, 2.15) for low birth weight. We found similar associations between each maternal mental disorder category and birth outcome, with slightly stronger associations for maternal mental disorders within the year prior to birth and for substance use disorder. The strongest association was found between maternal substance use disorder within the year prior to birth and low birth weight (RR=2.34, 95% CI: 2.16, 2.53). Conclusions: This large population-based study demonstrated an increased risk of preterm birth, low birthweight, perinatal mortality, and other adverse outcomes among births to Aboriginal women with mental disorders. Holistic perinatal care, treatment, and support for women with mental disorders may reduce adverse outcomes among Aboriginal births.