The court upheld the law, including the individual insurance mandate.
The long-awaited decision was read by Chief Justice John Roberts.
Most Americans oppose the law, even though they strongly support most of its provisions, according to a Reuters/Ipsos poll released on Sunday.
Fifty-six percent of the American people are against the health care overhaul and 44 percent favor it, according to the online poll conducted last week.
The survey results suggest that Republicans are convincing voters to reject Obama's reform even when they like much of what is in it, such as allowing children to stay on their parents' insurance until age 26.
Support for the provisions of the health care law was strong, with a full 82 percent of survey respondents, for example, favoring banning insurance companies from denying coverage to people with pre-existing conditions.
Sixty-one percent are in favor of allowing children to stay on their parents' insurance until age 26 and 72 percent back requiring companies with more than 50 employees to provide insurance for their employees.
A glaring exception to the popular provisions is the "individual mandate," which forces all U.S. residents to own health insurance.
Sixty-one percent of Americans are against the mandate, which was originally proposed by Republicans.
Additional coverage with reaction and analysis will be included in today's BizTimes Daily.