Parental depression is a risk factor for children’s healthy language development, however, the mechanisms of risk transmission are less understood. The present study aimed to examine aspects of parent-child interactions as mediators of the negative relations between mothers’ and fathers’ depression and children’s expressive language. Using longitudinal data from families in a large city of the Western United States (N = 497; child Mage = 5.83 months; 47% female), I examined these relations using mothers’ and fathers’ reports of depression, observations of mothers’ and fathers’ parent-child interactions, and observational indices of children’s expressive language in the home. Although results indicated no longitudinal relations between mothers’ or fathers’ depression and children’s expressive language, mothers’ depression was negatively related to mothers’ and fathers’ later parental supportiveness. Moreover, mothers’ acceptance and fathers’ supportiveness were positively related to children’s later expressive language. These findings shed light on family dynamics when mothers’ experience heightened levels of postpartum depression and how specific parent-child interactions support healthy language development.