The 5-foot-11, 186-pound Buchanon agreed to a two-year, $8.5 million contract, according to a source. The Bucs were trying to re-sign him. Earlier Wednesday, the Bucs agreed to a three-year, $8 million deal with Falcons defensive tackle Grady Jackson.
This will be the fourth team for Buchanon, who entered the NFL as a first-round pick of the Oakland Raiders in 2002. Buchanon spent three seasons with the Raiders. He went to the Texans in 2005 and 2006. The Bucs acquired him in 2006, and this was his best stop.
Buchanon started 29 games over the past two seasons. He had 113 combined tackles during those two seasons along with intercepting five passes. The Lions signed him with hopes that he is in his prime at the age of 28.
Buchanon started all 16 games for Tampa Bay last season, intercepting two passes and returning one for a touchdown. The Lions had only one interception by a defensive back in 2008.
John Clayton is a senior NFL writer for ESPN.com. Information from The Associated Press was used in this report.