This brief focuses on the health insurance coverage experiences under the Affordable Care Act (ACA) of mothers living with dependent children. Using 1997–2014 data from the National Health Interview Survey, we examine trends in uninsurance among mothers nationally and for mothers in states that did and did not expand Medicaid under the ACA by May 2014. We also assess changes from 2013 to 2014 in the characteristics of uninsured mothers and uninsurance rates for various subgroups of mothers, as well as reasons for being uninsured among mothers without coverage in 2014.