Rob Demovsky of ESPN.com provided the update Tuesday, noting the contract runs through 2019, which should give the organization "stability" in the top coaching role.
McCarthy has compiled a 121-70-1 regular-season record since taking over as the Packers' coach ahead of the 2006 campaign. He's also posted a 10-8 postseason mark, highlighted by Green Bay's Super Bowl XLV triumph over the Pittsburgh Steelers in 2011.
Although the Packers have been one of the league's best teams throughout his tenure, the 54-year-old Pennsylvania native's job status has come into question at times in recent years.
McCarthy defended himself against criticism and speculation about landing on the hot seat amid the team's struggles in November 2016.
"Let's just state the facts: I'm a highly successful NFL head coach," he told reporters. "With that, I've never looked at the ride to this point as smooth or whatever the words you used. To me, it's always bumpy, and to me that's the joy of it. That's this game. That's how hard it is in the NFL. Really, what you did last year or 2010, as we know, doesn't factor. It's even more so with the parity and the youth of the team."
In addition, Mike Florio of Pro Football Talk reported last year the relationship between McCarthy and superstar Aaron Rodgers was "inching closer to implosion." Florio noted if things broke down further someone would have to leave, and "it won't be the quarterback."
The situation didn't appear as tenuous throughout the 2017 season as Rodgers' collarbone injury reduced expectations for much of the year prior to his Week 15 return. The team finished 7-9 and missed the playoffs.
While there have been some rocky moments during his 12-year tenure, he usually puts the Packers in position to contend, and that's the objective of every coach when the season begins.
If the extension becomes official, he'll enter 2018 tied as either the second- or third longest-tenured head coach in the NFL with the New Orleans Saints' Sean Payton. They trail only Bill Belichick (New England Patriots) and Marvin Lewis, whose status is uncertain with the Cincinnati Bengals.