The extension comes hours after the Titans signed star left tackle Taylor Lewan to a five-year extension.
Terms of Walker's deal were not disclosed, but the contract is worth $17 million with $12.76 million guaranteed, including an $8 million signing bonus, a source told ESPN's Adam Schefter.
Lewan's deal was worth $80 million with $50 million guaranteed, making it the richest deal for an offensive lineman in terms of average annual value ($16 million) and guarantees, a source told Schefter.
Walker, 33, was selected to his third straight Pro Bowl last season when he led the Titans with 74 receptions and 807 receiving yards. He and the Kansas City Chiefs' Travis Kelce are the only tight ends with at least 800 receiving yards in each of the past four seasons.
The 2018 season will be Walker's 13th in the NFL and sixth in Tennessee. Over the past five seasons, he has 356 receptions -- the most by a tight end.
He spent the first seven seasons of his career with the San Francisco 49ers. He signed with the Titans as a free agent in 2013 and has 26 touchdown receptions, ranking 10th all-time in franchise history.
Walker has 479 receptions, 5,621 yards and 34 touchdowns in 12 NFL seasons.