The US Supreme Court is expected to hear arguments on California v. Texas on November 10, 2020. The plaintiffs in this case seeks to overturn the Affordable Care Act (ACA), a major piece of legislation that extended subsidized health insurance coverage and introduced new consumer protections like the elimination of pre-existing condition exclusions to millions of people across the country. In this brief, we estimate the consequences for Massachusetts of the Supreme Court overturning the ACA in its entirety. We find that as many as 422,000 Massachusetts residents would lose health insurance coverage, more than doubling the number of uninsured people. Massachusetts would lose $3.3 billion in federal health care spending that supports the state’s Medicaid program along with tax credits that help individuals afford insurance coverage.