Importance: Among adults with chronic disease, survivors of stroke have high out-of-pocket financial burdens. The US government enacted the Affordable Care Act (ACA) in 2010 and implemented the law in 2014 to provide more low-income adults with health insurance coverage. Objective: To assess whether ACA implementation is associated with cost-related nonadherence (CRN) to medication among adult survivors of stroke. Design, Setting, and Participants: This study analyzed data from the 2000 to 2016 National Health Interview Survey, an in-person household survey of the noninstitutionalized US population conducted annually by the National Center for Health Statistics. Conducted at the University of Michigan Medical School, Ann Arbor, from July 24, 2017, to February 28, 2018, the study had a sample of 13 930 survivors of stroke. Analyses were stratified by age (45-64 years vs ≥65 years). Time was treated as a continuous variable and as a categorical variable across 4 periods (2000-2005, historical control; 2006-2010, economic recession and peak unemployment; 2011-2013, before ACA implementation; and 2014-2016, after ACA implementation). Percentages are weighted to reflect US population estimates. Main Outcomes and Measures: The primary outcome was the self-report of CRN, defined as the inability to afford prescribed medications within the past 12 months. Results: Among the 13 930 total survivors of stroke, 38.1% were aged 45 to 64 years (50.5% were female and 49.5% were male, with a mean [SE] age of 56.0 [0.10] years), and 61.9% were aged 65 years or older (54.9% were female and 45.1% were male, with a mean [SE] age of 76.2 [0.09] years). From 2011 to 2013 through 2014 to 2016, Medicaid increased (from 24.0% [95% CI, 21.0%-27.2%] in 2011-2013 to 30.8% [95% CI, 27.3%-34.6%] in 2014-2016; P < .001) and uninsurance decreased (from 13.7% [95% CI, 11.3%-16.4%] to 6.8% [95% CI, 5.3%-8.8%]; P < .001) among survivors of stroke aged 45 to 64 years. Among survivors aged 45 to 64 years, CRN increased over time before ACA implementation (from 18.6% [95% CI, 16.5%-20.9%] in 2000-2005, to 22.6% [95% CI, 19.7%-25.9%] in 2006-2010, to 23.8% [95% CI, 20.7%-27.3%] in 2011-2013) and decreased after ACA implementation to 18.1% (95% CI, 15.4%-21.3%; P = .01) in 2014 to 2016. The period after ACA implementation was associated with lower odds of CRN after adjustment for sociodemographics, year, and clinical factors (odds ratio [OR], 0.63; 95% CI, 0.47-0.85). The difference was attenuated after further adjustment for health insurance coverage (OR, 0.76; 95% CI, 0.56-1.03). Conclusions and Relevance: After the ACA implementation, health insurance coverage increased and CRN decreased among adult survivors of stroke, suggesting that further expansion of Medicaid coverage is likely to be advantageous for survivors.