The Patriots acquired Haynesworth from the Washington Redskins for a 2013 fifth-round draft pick shortly after the lockout ended.
In his 10th pro campaign, Haynesworth did little for the Patriots this season, totaling just three tackles in six games.
The Bucs released defensive tackle John McCargo to clear a roster spot for Haynesworth.
On Monday, they placed defensive tackle Gerald McCoy on injured reserve with a torn right biceps, subsequently ending the 2010 first-round draft pick's season.
Haynesworth made headlines in 2009 when he signed a seven-year, $100 million deal with the Redskins after starring for seven years with the Tennessee Titans.
But he played just 20 games over two seasons in a Redskins uniform.
The 30-year-old University of Tennessee product has 30 1/2 career sacks and 327 tackles over 116 career games. He posted a career-high 8 1/2 sacks and 51 tackles from a defensive tackle spot in his final season of 2008 with the Titans.