The deal is for two years and $23 million, a source told ESPN.
McCourty made the announcement on his "Double Coverage" podcast with his twin brother, Jason, who had the option in his contract picked up last week to return to the Patriots in 2020.
Staying in New England with his brother was a priority for Devin, who turns 33 on Aug. 13.
"Breaking news! Breaking news!" Devin McCourty said on the podcast. "I will be staying here in New England. Sign me up."
The Patriots released a statement later on Sunday saying they've "extended the contract of safety Devin McCourty."
McCourty was part of three Super Bowl championship teams with the Patriots.
The 2010 first-round draft choice out of Rutgers quickly elevated as a top leader with the Patriots, as he was voted a captain by teammates in just his second season -- a role he continued to have for nine consecutive years.
Lauded by coach Bill Belichick for his intelligence and as a solidifying presence in the secondary, McCourty missed just five games over 10 seasons in New England, a reflection of his durability and consistency while being tapped to fill multiple roles on defense and special teams.
McCourty, who played in four Pro Bowls, totaled 26 interceptions in the regular season, adding two more in the postseason.
He has been credited with 772 career regular-season tackles, with 86 passes defended, 12 forced fumbles and three sacks. In the playoffs, he amassed 111 tackles and 10 passes defended.