Thomas caught 665 passes in nine seasons with the Broncos from 2010-18.
Thomas played in Denver for the first nine years of his career from 2010-18. The former No. 22 overall pick was a four-time Pro Bowler with the Broncos and tallied 665 receptions and 62 touchdowns.
The Georgia Tech product was traded to Houston in October 2018, but was released by the Texans on Feb. 12. He tore his left achilles during a Week 16 matchup with the Eagles in December 2018 and was carted off the field in the fourth quarter at Lincoln Financial Field in Philadelphia.
Thomas will join Patriots offensive coordinator Josh McDaniels in New England. The pair was together for a short stint in Denver in 2009 and 2010 before McDaniels was fired in November 2010.
New England won its sixth Super Bowl of the Brady-Belichick era in 2018 with a 13-3 win over the Rams in Super Bowl LIII.
Running back James White led the Patriots with 87 receptions last season. Tight end Rob Gronkowski retired on March 24.