Sources told ESPN that the Patriots will receive a conditional seventh-round pick in the 2020 NFL Draft in return. The trade is pending a physical.
Hollister made the Patriots' roster as an undrafted rookie out of Wyoming in the 2017 campaign. He played in 15 regular-season games as a rookie and had a large role on special teams.
The 25-year-old tight end was limited by injuries last season. Hollister has recorded eight catches for 94 yards over two NFL seasons.
"He has a lot of football in front of him," Patriots head coach Bill Belichick told reporters last off-season. "He didn't have a lot of experience -- had some -- but has gained a lot and will gain a lot more. I think he's got a great future. He works hard, he's a tough kid, he plays hard, practices hard and has become much better at his fundamentals and techniques at his position."
After the retirement of Rob Gronkowski this off-season, the Patriots are left with potential starter Austin Seferian-Jenkins, Stephen Anderson, Matt LaCosse and Ryan Izzo at the tight end spot. Hollister joins a Seahawks roster that includes Will Dissly, Nick Vannett, Tyrone Swoopes and Ed Dickson at the position.