Clayton, the 2004 NFL Offensive Rookie of the Year who has struggled since that strong debut, agreed to the contract two days after becoming an unrestricted free agent.
As a rookie, Clayton, a first-round draft pick from LSU (15th overall) had 80 catches for 1,193 yards and seven touchdowns -- the fifth-best first season in league history.
But Clayton's production fell off after that and he lost his starting job at times. He did start nine games last season after Joey Galloway was injured.
In the last four years, he's been plagued by injuries and inconsistency, and his best year was 2008, when he had 38 receptions for 484 yards and one touchdown.
Clayton did play well in the season finale, though, with two catches for 87 yards, one a 58-yard TD -- his only score of the season.
The 26-year-old, who has scored just two touchdowns since his rookie season, has 205 career catches for 2,706 yards and nine TDs.
The deal means the Bucs, who are rebuilding under new coach Raheem Morris, will return both starting receivers from last season. Last week, the team placed the franchise tag on Antonio Bryant, assuring him a one-year contract worth $9.88 million.