Cpl. Wassef Ali Hassoun is safe and appears to be in good health, said a Pentagon official, speaking on condition of anonymity.
In making the announcement about Hassoun, State Department spokesman Richard Boucher said in Washington: "We were able to go get him."
When reached at his West Jordan, Utah, home Thursday morning, Hassoun's brother, Mohamad, said he had no comment.
Contradictory reports have surrounded the fate of the 24-year-old Lebanese native since his disappearance June 20.
On Saturday, a statement posted on a Web site known for extremist Muslim comment said Hassoun had been beheaded. A day later, another Web statement declared he had not been killed.
An Iraqi militant group said Monday it was holding him in a safe place but hadn't killed him. Al-Jazeera television broadcast the statement from "Islamic Response," which claimed responsibility June 27 for Hassoun's kidnapping.
NBC reported the Navy was investigating whether his disappearance may be part of a kidnapping hoax. A Marine spokesman confirmed the Navy investigation remains open.
"I don't think they're ruling that out. It would be fair to say they're not ruling that out," Maj. Nat Fahy said earlier Thursday.
A spokesman for the Bahrain-based U.S. Navy's 5th Fleet said the "matter is under investigation by Naval Criminal Investigative Service" and referred further questions to the service in Washington. A call to the service seeking comment was not immediately returned.
One Pentagon official told CBS News Correspondent David Martin that Hassoun "better have a good story."
Reports emerged he might have been freed after his family in Utah said Tuesday they had word that he had been released and was safe, but they didn't know where.
Earlier, a Lebanese Foreign Ministry official, speaking on condition of anonymity, said Hassoun "is with his parents" in northern Lebanon. But journalists gathered outside the family's Tripoli home saw no sign of Hassoun.
Hassoun's brother, Sami, refused to confirm or deny the information when reached by the AP for comment.
On Tuesday, he said someone had visited the family in northern Lebanon and told them his brother was free and well. A Lebanese government official said Wednesday the kidnappers released Hassoun after he pledged he would not return to the U.S. military.
Two FBI agents met with the Hassoun family in Utah for about 20 minutes Wednesday. The agents were not there to deliver any news to the family, but instead were sent to determine where the family was getting its information about Hassoun's whereabouts, agent Kelly Kleinvachter said.
The Marines said Hassoun disappeared on "unauthorized leave," but changed his status to "captured" after he turned up June 27 on television blindfolded with a sword hanging over his head.
Some reports also have said Hassoun fled his camp near the restive Iraqi city of Fallujah after seeing one of his colleagues killed by a mortar shell; others indicated he was lured out and captured.
Some of those claiming to be the captors have said he was romantically involved with an Arab woman and was lured away from his Marine base and captured. There also were reports that Hassoun, who was educated at American schools in Lebanon before moving to Utah and joining the Marines, might have been trying to get to Lebanon when he was captured.
Earlier Thursday, no overt signs of joy or preparations to welcome Hassoun could be seen at the family residence in Tripoli, an apartment on the second floor of a six-story building in the low-income Abu Samra district of Lebanon's second-largest city.
For Hassoun to make his way to Lebanon from Iraq, about 500 miles away, he would have to travel through Syria, which borders Iraq's western Anbar province, where his unit, the 1st Marine Expeditionary Force, is based. Hassoun worked as a translator.
The United States has accused Syria of not doing enough to prevent militants from infiltrating its border to Iraq to fight U.S. and allied forces.
Syria is the main power broker in Lebanon, where it keeps thousands of troops. There are no direct flights from Iraq, and another possible route, through U.S.-allied Jordan, is unlikely because he could end up with the Americans.
In a related story, there is still no word on the fate of Spc. Keith "Matt" Maupin, a 20-year old Ohio native who disappeared after an ambush on a convoy west of Baghdad on April 9.
The killing of Maupin was reported by Arab television, which aired a videotape showing a blindfolded man identified by his captors as Maupin sitting on the ground.
Al-Jazeera said that in the next scene, gunmen shoot the man in the back of the head, in front of a hole dug in the ground. The station did not broadcast the killing.
No body has been found and the Army says it has no confirmation of Maupin's death. He continues to be officially listed as captured.