Using the Fragile Families and Child Wellbeing Study, we examine the association between parental major depressive and generalized anxiety disorders and child behavior problems across family types: married, cohabiting, involved nonresident father, and noninvolved nonresident father. Among 3-year-olds in all families, maternal anxiety/depression is associated with increased odds of anxious/depressed, attention deficit, and oppositional defiant disorders (N = 2,120). Paternal anxiety/depression has no significant association with these problem behaviors; father's illness, however, exacerbates anxious/depressed behaviors in young children if both parents are ill and he is coresident. The findings underscore the importance of maternal mental health for child well-being and suggest that a negative interaction between parent illnesses is most likely when parents and children share the same disorder.