Using data drawn from a longitudinal study of families of children with ASD, the current study examined the impact of marital quality on three indicators of maternal psychological adjustment: depressed mood, parenting efficacy, and subjective well-being. Multiple regression analyses indicated marital quality to be a significant cross-sectional and longitudinal predictor of maternal adjustment. In the cross-sectional regressions, marital quality negatively predicted maternal depression and positively predicted parenting efficacy, and well-being, while in the longitudinal regressions, initial levels of marital quality negatively predicted maternal depressed mood and positively predicted well-being at follow-up. Longitudinal regression results also revealed that marital quality mediated the relationship between family SES and maternal well-being. Study limitations and implications are discussed.