Affordable Care Act provisions implemented in 2010 required insurance plans to offer dependent coverage to people ages 19–25 and to provide targeted preventive services with zero cost sharing. These provisions both increased the percentage of young adults with any source of health insurance coverage and improved the generosity of coverage. We examined how these provisions affected use of the human papillomavirus (HPV) vaccine, which is among the most expensive of recommended vaccines, among young adult women. Using 2008–12 data from the National Health Interview Survey, we estimated that the 2010 policy implementation increased the likelihood of HPV vaccine initiation and completion by 7.7 and 5.8 percentage points, respectively, for women ages 19–25 relative to a control group of women age 18 or 26. These estimates translate to approximately 1.1 million young women initiating and 854,000 young women completing the vaccine series.