The 6-foot-5, 262-pound pass-catcher will step into a new-look Patriots tight ends room, following the retirement of All-Pro Rob Gronkowski.
Seferian-Jenkins, 26, was a second-round pick by the Tampa Bay Buccaneers in the 2014 NFL Draft. He played for two seasons in Tampa Bay, before being waived in 2016. The New York Jets claimed Seferian-Jenkins three days later.
Seferian-Jenkins signed a two-year, $10 million contract with the Jacksonville Jaguars in 2018. He had 11 catches for 90 yards and a touchdown in five starts last season. The Jaguars declined Seferian-Jenkins' team option for 2019 in February, sending him to free agency.
The Washington product had a career-high 50 catches in 2017 with the Jets. He turned those receptions into 357 yards and three scores. Seferian-Jenkins had a career-high four scores during his 2015 campaign with Tampa Bay. The veteran tight end has 116 receptions for 1,160 yards and 11 scores in 43 career appearances.