The controversial law, which fulfills a promise to expand health care to a majority of Americans, has been President Obama's signature legislation in office.
"Today's decision was a victory for people all across this country whose lives will be more secure," Obama said at a briefing shortly after the ruling.
The decision, however, does not mean an end to efforts to overturn or weaken the law, as opponents vowed to keep working on its repeal.
The court ruled that the centerpiece of the law, the individual mandate, could be upheld under the federal government's taxing authority. In other words, the government can't force people to buy health insurance, but it can give them a tax penalty if they don't.
The court has also limited the part of the act that would have expanded the coverage to uninsured Americans through Medicaid.
WebMD talked with health care experts about how the landmark decision will impact health care consumers.
Does the Supreme Court's ruling mean the debate over health care reform is over?
No. House Speaker John Boehner (R-Ohio) said the House would vote to fully repeal the law on July 11. Regardless of the outcome of that vote, though, it would be highly unlikely that the repeal would get through the Senate. In a speech soon after the ruling, Senate Minority Leader Mitch McConnell called for a repeal of the entire law. Presumptive Republican presidential nominee Mitt Romney has said he will repeal the law if elected.
What are some changes that have already taken place because of the law?
About 3.1 million young adults gained health insurance through a provision that allows them to stay on their parents' policies until age 26. In addition, nearly 62,000 Americans with pre-existing health conditions, who would otherwise be uninsurable, gained coverage through the government's Pre-Existing Condition Insurance Plans (PCIPs). Those enrolled will be able to stay in the program until it expires in 2014. At that time, they'll be eligible to buy health insurance through state-based insurance marketplaces scheduled to be up and running by fall 2013.
Other consumer protections already in effect include:
The right to appeal an insurer's decision
Preventive care with no co-pay
Guaranteed insurance coverage for children under the age of 19 with pre-existing conditions
No more lifetime limits on health insurance spending
Review of suspected unreasonable insurance rate increases
The requirement that insurance companies spend at least 80% of the money they collect on medical expenses (this 80/20 rule so far means 12.8 million Americans will participate in $1.1 billion in rebates from insurance companies this summer, according to the HHS)