National Security Adviser Susan Rice said Peter Theo Curtis, who was kidnapped by militants near the Syria-Turkey border in October 2012, "is now safe outside of Syria," Xinhua reported.
"Today, we join his family and loved ones in welcoming his freedom," Rice said in a statement. "We expect he will be reunited with his family shortly."
The news came after another US journalist James Foley, who was abducted by militants in Syria in November 2012, was beheaded by the Islamic State (IS) as shown in a video released online early last week by the militant group.
The IS, which has seized a large swath of territory in western and northern Iraq in recent months, also threatened to kill another man shown on the video said to be American freelancer Steven Sotloff to avenge ongoing US airstrikes on its targets in northern Iraq.
Peter Theo Curtis, who was kidnapped by militants in Oct 2012
"Just as we celebrate Theo's freedom, we hold in our thoughts and prayers the Americans who remain in captivity in Syria," Rice said. "As President (Barack) Obama said, we have and will continue to use all of the tools at our disposal to see that the remaining American hostages are freed."
The Obama administration sent special operations troops into Syria this summer to rescue Foley and other American hostages, but failed to find them, officials told the press.
The US fighter jets on Sunday conducted two air raids on IS targets, destroying a Humvee near the Mosul Dam and an armed vehicle near Erbil, capital of Iraq's autonomous Kurdish region, the US central command said in a statement.
It said the US military has conducted a total of 96 airstrikes in Iraq since Aug 8, a day after Obama gave the order.