Background: Parent substance use disorders (SUDs) can have negative impacts on children, including lower socioeconomic status and more difficulties in academic and social settings and family functioning when compared with children living with parents without an SUD. Method: This report uses data from the 2009 to 2014 National Surveys on Drug Use and Health (NSDUHs) to determine the number of children living with a parent who had an SUD (alcohol use disorder or illicit drug use disorder). The analysis is based on a sample size of 22,200 adults aged 18 or older with at least 1 related child aged 17 or younger residing in the household. Results: Based on combined 2009 to 2014 NSDUH data, about 8.7 million (12.3 percent) children aged 17 or younger lived in U.S. households with at least one parent who had an SUD. About 7.5 million (10.5 percent) children lived in households with at least one parent who had an alcohol use disorder, and about 2.1 million (2.9 percent) children lived in households with at least one parent who had a past year illicit drug use disorder. Conclusion: The annual average of 8.7 million children aged 17 or younger living in U.S. households with at least one parent who had an SUD highlights the potential breadth of substance use prevention and treatment needs for the whole family—from substance abuse treatment for the affected adults and prevention and supportive services for the children.