This article reviews the literature on factors affecting toddler cognitive development in low-income families. It discusses a model in which maternal factors, such as knowledge of child development, stress, and depression, influence the quality of mother–child interaction, which in turn influences the child's cognitive development. The results of a recent study of 84 low-income mothers and their toddlers are then summarized. This study both supported and contradicted the suggested model. As expected, observed maternal supportiveness of the child during mother–child interaction directly influenced child cognitive competence. Maternal knowledge of child development and maternal stress affected child cognitive competence indirectly, by influencing maternal supportiveness. Contrary to expectations, maternal depressive symptoms were not associated with maternal supportiveness or child cognitive development. The findings suggest that intervention programs with low-income families that improve maternal knowledge, reduce maternal stress, and promote maternal supportiveness of the infant during mother–child interaction, may improve child cognitive development. The lack of associations with maternal depression suggests that care providers may need to consider whether other attitudes and expectations of the mothers, perhaps learned in childhood, may influence both their reports of depressive symptoms specifically, and the quality of their parenting, more generally.