McCoy's agent, Orlando Castano Jr., confirmed the contract's amount to The Associated Press on Wednesday.
The deal includes an undisclosed signing bonus.
McCoy, a second-round pick of the Philadelphia Eagles in the 2005 draft, played in 12 games, including two starts, for the Bucs last season. It was his second season with the Buccaneers. He finished the 2007 season with the New Orleans Saints.
The former San Diego State star has made 97 tackles and forced three fumbles in 47 NFL games, 12 of them starts. He has made another 50 tackles on special teams.
It was the Seahawks' third move in the last three days on defense. They re-signed pass rusher Darryl Tapp on Monday, then traded him to the Eagles for defensive end Chris Clemons and a fourth-round pick in next month's draft Tuesday.
Copyright 2010 by The Associated Press