A mother’s experience of violent injury represents a sentinel event with repercussions for her child’s well-being. We aimed to measure and compare mental health service utilization among children exposed to a mother who experienced assault versus those unexposed.

We conducted a population-based matched cohort study of children (< = 18 years) and their mothers residing in Ontario, Canada, 2005–2023. The main exposure was a mother’s experience of assault-related injury, defined as any emergency department (ED) visit, hospitalization, or death during the child’s lifetime. Children were age-, sex-, and maternal age-matched 1:4 to unexposed children. The main outcome was child mental health service utilization (outpatient, ED, or hospitalization) within the five years following the mother’s injury. Modified Poisson regression models estimated adjusted rate ratios (aRRs) controlling for sociodemographic and health factors.

There were 79,496 exposed and 315,755 unexposed children (52.5% male, median age at index 7 years [IQR 3-11]). Compared to those unexposed, exposed children had higher mental health service utilization across all settings including hospitalizations (2.9% versus 1.2%; aRR 2.02, 95% CI 1.85–2.20), ED visits (8.0% versus 3.8%; aRR 1.87, 95% CI 1.77–1.98), and outpatient visits for substance-use disorder (1.2% vs. 0.5%; aRR 2.05, 95% CI 1.56–2.69).

Children exposed to maternal violent injury were at greater risk of mental health service utilization than unexposed children. Findings emphasize the ripple effects of violence on the children and the need for enhanced mental health support to children of mothers affected by violence.