A source told ESPN NFL Insider Adam Schefter that the one-year deal is for $3 million.
The 34-year-old Fitzpatrick, who has started 116 games over his 12 seasons in the NFL, will serve as the backup to starter Jameis Winston. Fitzpatrick is coming off a two-year run with the New York Jets that was marked by one terrific season, a long contract dispute and one disappointing season.
The Bucs will be the seventh NFL stop for Fitzpatrick, who has also played for the Rams, Bengals, Bills, Titans and Texans. According to the Elias Sports Bureau, only five quarterbacks -- Jeff Blake, Steve Bono, Chris Chandler, Gus Frerotte and Vinny Testaverde -- have thrown a pass for seven teams.
Technically Fitzpatrick became a free agent on Feb. 10, when his contract automatically voided. The contract, signed on the eve of last training camp, paid him $12 million for one season.
He received a raise after a career season in 2015. After replacing the injured Geno Smith in the preseason -- a teammate broke Smith's jaw in a locker room altercation -- Fitzpatrick led the Jets to 10 wins and set the franchise record with 31 touchdown passes.
It was a contract year for Fitzpatrick, and though there was mutual interest in another deal, it took a six-month stalemate before the two sides reached an agreement. The Jets were reluctant to commit to a long-term deal because they felt his 2015 performance might have been an aberration.
In 2016, Fitzpatrick was benched twice, threw 17 interceptions and 12 touchdowns and compiled a league-low passer rating (69.6) as the Jets stumbled to 5-11. The low point was a Week 3 loss in Kansas City, when he threw six interceptions.
At the end of the season, Fitzpatrick acknowledged that his starting days in the NFL were probably over, but he expressed a strong interest in resuming his career.
Fitzpatrick, who entered the league as a seventh-round pick of the Rams in 2005, is 46-69-1 as a starter while playing for six teams. He has 166 touchdown passes, 133 interceptions and has thrown for 25,888 yards, 14th on the active list.
ESPN's Rich Cimini contributed to this report.