The Patriots will be Brown's third team this year. He was traded from the Pittsburgh Steelers to the Raiders in March.
Brown reacted to the move on Twitter:
Brown's tenure with the Raiders turned into a massive failure in a short amount of time. The 31-year-old missed the start of training camp because of frostbite caused by wearing the wrong footwear in a cryotherapy machine.
Brown also filed two different grievances with the NFL—which he lost—over the type of helmet he wanted to wear during games.
On Wednesday, Brown used social media to post and respond to a letter he received from Raiders general manager Mike Mayock informing him of nearly $54,000 in fines in relation to a missed practice and walkthrough.
Schefter reported Thursday the team was planning to suspend Brown following an altercation with Mayock.
But Raiders head coach Jon Gruden told reporters Friday that Brown would play in Week 1 against the Denver Broncos. Oakland also fined the four-time All-Pro for conduct detrimental to the team, which voided the guaranteed money in his contract and prompted him to ask for his release.
Adam Schefter @AdamSchefter
In addition to fining Antonio Brown $215,073.53 for conduct detrimental to the team that voided $29.125 million worth of guaranteed money in his contract, the Raiders sent Brown a letter that he no longer will be entitled to termination pay if they release him, per sources.
Brown wrote in an email to ESPN's Jeff Darlington that he was not going to play "after they took [away my guarantees] and made my contract week-to-week."
The Raiders granted Brown's wish by releasing him.
Brown is one of the most productive players in the NFL. He's had at least 100 receptions, 1,200 receiving yards and eight touchdowns in each of the past six seasons.
The Patriots are one of the few teams that makes sense as a landing spot for Brown. They've got a history of helping star players rehab their images while also reaping the benefits of their talents on the field.
Their strong infrastructure, starting with head coach Bill Belichick, allows them to take bold risks. They've also shown in the past how quickly they will move on from a player if they feel he isn't fitting in with their system.
Brown and Tom Brady could make for a lethal pairing, especially as the Patriots explore ways to replace Rob Gronkowski's production. If Brown doesn't cause any problems, a receiver tandem of him and Josh Gordon will be scary for opposing defenses.