When children are exposed to physical, sexual, or psychological harm to their mothers, or the aftermath of these assaults, they are more likely to experience poorer developmental outcomes. Evidence on the nature and strength of the relationship between exposure to intimate partner violence (EIPV)/family violence (EFV) and childhood outcomes lacks consensus, due to methodological limitations and lack of Canadian-based evidence. The objective of this research was to provide evidence on the relationships between EIPV/EFV and children’s developmental health to bring the current literature to more of a consensus. The study examined developmental vulnerability at Kindergarten of children prenatally and/or postnatally exposed to maternal intimate partner violence (IPV)/family violence (FV) victimization as recorded in the Manitoba provincial justice system compared to unexposed counterparts. Using linked longitudinal, whole-population administrative data from the Manitoba Population Research Data Repository housed at the Manitoba Centre for Health Policy (MCHP), three separate cohorts of children living in Manitoba, Canada were constructed based on the maternal IPV/FV victimization exposure periods (Cohort 1: during pregnancy; Cohort 2: child age 0 to 5 years; Cohort 3: pregnancy to child age 5 years) and retrospectively followed. Multiple logistic regression models were then constructed, adjusting for maternal and child characteristics. Prenatal EIPV/EFV and developmental vulnerability at Kindergarten did not show significant relationships with developmental vulnerability domains after adjusting for the covariates (Cohort 1 n = 927). After adjusting for the covariates, children postnatally exposed to maternal IPV/FV victimization as well as those exposed prenatally and postnatally had higher odds of being developmentally vulnerable in social competence, emotional maturity, and two or more domains (Cohorts 2 n = 5,321; Cohort 3 n = 5,874). The observed relationships between EIPV/EFV and developmental vulnerability at Kindergarten varied based on exposure periods and developmental domains. This study adds Canadian-based evidence to the current knowledge and addresses methodological limitations by employing a robust longitudinal study design. The findings will aid researchers’, various stakeholders’, and the public’s understanding of potential burdens of EIPV/EFV and suggest the relevance of tailoring interventions and support systems for intergenerational victims of IPV/FV based on the timing of violence.