Thurman missed the 2006 and 2007 seasons because of violations of the NFL's substance abuse policy. He tried to come back in 2007, but the league drug counselors did not rule in his favor.
Though Goodell said at the NFL owners meetings that he didn't have to rule on Thurman until around the start of training camp, Goodell gave Thurman permission to train at the Bengals' facility this offseason. He also mentioned he was pleased with Thurman's progress.
"Odell has met the NFL's conditions for reinstatement and has been added to our offseason roster," Bengals head coach Marvin Lewis said. "It is now up to Odell to continue to meet all NFL guidelines, and to maintain a standard of personal responsibility that will allow him the chance to compete for a spot on our team."
Bengals president Mike Brown's support for Thurman during the player's time of punishment wasn't lost on teammate Willie Anderson.
"I saw a side of Mr. Brown, a compassionate side, and he has done everything to help this man [Thurman] earn a living for himself and his family," Anderson, a veteran offensive tackle, told the Cincinnati Enquirer for Tuesday's editions.
Thurman's reinstatement comes less than three weeks after the Bengals cut wide receiver Chris Henry following his fifth arrest since 2005. Henry was suspended by Goodell for the first half of the 2007 season for misconduct.
Thurman will now be allowed on the field with the Bengals for camps starting in May.
In recent months, Thurman has been working out near his home in Monticello, Ga., and also at the University of Georgia in nearby Athens.
Because of injuries and Thurman's suspension, linebacker had been a star-crossed position for the Bengals the past two seasons. At one point in 2007, the team was forced to switch defensive end Robert Geathers to outside linebacker because of the shortage of bodies.
Cincinnati's coaches, including new defensive coordinator Mike Zimmer, have discussed the possibility of converting to a 3-4 front in 2008, and that could create an opening for Thurman at inside linebacker.
"The offseason is a chance to get to know guys," Bengals linebacker Dhani Jones, speaking to the Cincinnati Enquirer, said of Thurman. "He works hard. The linebacker position will have some significant competition with [Thurman] coming back. It's great to have him back in the mix."
Lewis had suggested last spring, when it appeared that Thurman would be permitted to return after sitting out the 2006 season, that the linebacker would have a chance to win back a spot on the roster, and that the Bengals had not given up on him.
Last July, the league denied Thurman's application for reinstatement.
A starter in 2005 when he led the Bengals in tackles as a rookie, Thurman was initially suspended for four games in 2006 when he missed a scheduled drug screening. The sanction was subsequently increased to a year after Thurman was arrested on DUI charges Sept. 25, 2006.
Citing confidentiality guidelines, league and team officials declined to say last July why Thurman was not cleared then for reinstatement.
Two men in Monticello, Ga., filed a complaint last spring, alleging Thurman kicked and hit them at a party two days after he settled his drunken driving case in Cincinnati. The men later dropped their complaint, and no charges were filed.
Despite missing much of his rookie training camp because of a protracted contract impasse, Thurman appeared in 15 games in 2005, all as a starter, and registered 148 tackles, one sack, five interceptions, nine passes defensed and four forced fumbles. The former Georgia star, a second-round draft pick in 2005, was a candidate for defensive rookie of the year honors.
Thurman has two years left on his original rookie contract with the Bengals. The deal would pay him $520,000 in 2008 and $615,000 in 2009. He lost $785,000 in salary during his two-year suspension.
John Clayton is a senior NFL writer for ESPN.com. ESPN.com senior NFL writer Len Pasquarelli and The Associated Press contributed to this report.