Parental substance use is a well-documented risk for children. However, little is known about specific effects of prenatal and postnatal substance use on child maltreatment and foster care placement transitions. In this study, the authors unpacked unique effects of (a) prenatal and postnatal parental alcohol and drug use and (b) maternal and paternal substance use as predictors of child maltreatment and foster care placement transitions in a sample of 117 maltreated foster care children. Models were tested with structural equation path modeling. Results indicated that prenatal maternal alcohol use predicted child maltreatment and that combined prenatal maternal alcohol and drug use predicted foster care placement transitions. Prenatal maternal alcohol and drug use also predicted postnatal paternal alcohol and drug use, which in turn predicted foster care placement transitions. Findings highlight the potential integrative role that maternal and paternal substance use has on the risk for child maltreatment and foster care placement transitions.