The decision handed Obama a campaign-season victory in rejecting arguments that Congress went too far in requiring most Americans to have health insurance or pay a penalty.
Chief Justice John Roberts announced the court's judgment that allows the law to go forward with its aim of covering more than 30 million uninsured Americans.
The Supreme Court has ruled that the mandate is constitutional and survived as a tax. The Medicaid provision is limited but not invalidated.
An in depth story is to follow.
To read the actual opinion click here.