This brief focuses on the health insurance coverage experiences under the Affordable Care Act (ACA) of fathers living with dependent children. Using 1997-2014 data from the National Health Interview Survey, we examine trends in uninsurance among custodial fathers nationally and in states that did and did not expand Medicaid under the ACA by May 2014. We also assess changes between 2013 and 2014 in the characteristics of uninsured custodial fathers and uninsurance rates for various subgroups of fathers as well as reasons for being uninsured among those without coverage in 2014. We find an increase in uninsurance among custodial fathers between 1997 and 2013, followed by a decline between 2013 and 2014, with larger reductions found in Medicaid expansion states compared to states that did not expand Medicaid. More than five million custodial fathers remained uninsured in 2014.