This research examines the relationship between maternal employment and child overweight among fifth grade Hispanic and non-Hispanic white children. Data from the Early Childhood Longitudinal Study Kindergarten (ECLS-K) cohort fifth grade sample (N = 4,360) were analyzed. OLS regression models were estimated predicting percentile BMI as a function of maternal employment, ethnicity, parental nativity status, income, and the interactions of employment, ethnicity/nativity, and income. Among Hispanic children of immigrants, maternal employment is associated with lower percentile BMI and this association strengthens at higher levels of income. Among Hispanic children of natives and non-Hispanic whites, maternal employment is beneficial (i.e. associated with lower percentile BMI) among low-income children but detrimental among high-income children, but this pattern is significantly greater in strength for Hispanics than non-Hispanic whites. Thus, maternal employment is associated with worse health outcomes only in the case of Hispanic children of natives, and maternal employment is associated with the best outcomes for Hispanic children of mothers from high-income families. We speculate that among children of immigrants, maternal employment may signify and/or accelerate assimilation towards middle- or upper-class American values of healthy weight and body size. Diet, meal regularity and supervision, and childcare did not mediate the relationship between maternal employment and overweight.