Background: Children of parents with intellectual impairment are thought to be at risk for poor social-emotional well-being. This study investigated the relationship between maternal intellectual impairment and poor child social-emotional well-being. Method: Secondary analysis of data from waves 2-4 of the Millennium Cohort Study (UK). Social-emotional well-being was measured by maternal report at Waves 2-4, with teacher and child self-report at Wave 4. Bivariate and multivariate analyses were conducted. Results: Unadjusted, maternal intellectual impairment was associated with an elevated risk of overall poor social-emotional well-being at ages 3 and 5, but not at age 7. After controlling for individual, family and environmental characteristics, no statistically significant association was found between maternal intellectual impairment and poor child social-emotional well-being. Conclusions: Children of mothers with intellectual impairment are more likely than their peers to be exposed to adverse living conditions. These living conditions may explain, at least in part, why these children face a heightened risk of poor social-emotional well-being at ages 3 and 5. Improving the living conditions of mothers with intellectual impairment may offer a pathway to child social-emotional well-being.