Background: Children with intellectual disability (ID) have been found to be at an increased risk for developing behavioural problems. The purpose of this study was to examine the relationship between the marital domain, including marital quality and spousal support, and behaviour problems in children with and without ID. Methods: The relationship between the marital domain and child behaviour problems was examined in 132 families of 6-year-olds with and without ID. Using hierarchical regression, these relationships were also studied over time from child ages 6-8 years. Child behaviour problems were assessed with mother-reported Child Behavior Checklist. The marital domain was measured using the Dyadic Adjustment Scale-7 and the Spousal Support and Agreement Scale. Mother-reported parenting stress and observed parenting practices were tested as potential mediators of the relationship between the marital domain and child behaviour problems. Results: Mean levels of the marital domain were not significantly different between typically developing (TD) and ID groups, but there were significantly greater levels of variance in reported marital quality in the ID group at ages 6, 7 and 8. The marital domain score at child age 6 years predicted child behaviour problems at age 8 for the TD group only. This predictive relationship appeared to be a unidirectional effect, as child behaviour problems at age 6 were not found to predict levels of the marital domain at age 8. Parenting stress partially mediated this relationship for the TD group. Conclusions: The marital domain may have a greater impact on behavioural outcomes for TD children. Implications for future research and interventions are discussed.