Background: Maternal stress and depression are associated with infections in offspring, but there is a paucity of data for other mental disorders. Methods: We conducted a retrospective cohort study of 832,290 children born between 2006 and 2016 in hospitals of Quebec, Canada. We identified maternal mental disorders before and during pregnancy, and admissions for otitis media, pneumonia, infectious enteritis and other infections in children before 13 years of age. We used Cox proportional hazards regression to estimate hazard ratios (HRs) with 95% confidence intervals (CI) for the association between maternal mental disorders and the risk of pediatric infectious diseases, adjusted for maternal age, comorbidity, socioeconomic disadvantage, and other confounders. Results: The incidence of pediatric infection hospitalization was higher for maternal mental disorders compared with no disorder (66.1 vs. 41.1 cases per 1000 person-years). Maternal mental disorders were associated with 1.38 times the risk of otitis media (95% CI: 1.35-1.42), 1.89 times the risk of bronchitis (95% CI: 1.68-2.12), and 1.65 times the risk of infectious enteritis in offspring (95% CI: 1.57-1.74). Stress and anxiety disorders (HR 1.49, 95% CI: 1.46-1.53) and personality disorders (HR 1.55, 95% CI: 1.49-1.61) were more strongly associated with the risk of pediatric infection hospitalization than other maternal mental disorders. Associations were prominent in the first year of life and weakened with age. Conclusions: Maternal mental disorders are risk factors for infectious disease hospitalization in offspring. Women with mental disorders may benefit from psychosocial support to reduce the risk of serious infections in their children.