Brown, 32, joined Seattle in 1997 as an unrestricted free agent from Pittsburgh and led the Seahawks in tackles from 1997-99.
"You've got to establish a core group of players that you really want here as long as I'm here, certainly, so they can finish their careers as Seahawks," said Coach and General Manager Mike Holmgren. "Chad is one of those players, so we have been working on this for a while and will continue to do it (with other veterans)."
Since arriving, he has started all 78 games he's played, missing one game in 1997 and '99, and no Seahawks player has more tackles than his 571 over that span.
He averages 114 tackles per year, which ranks him 10th all-time on the Seahawks list, and is just 119 tackles away from moving into fifth place ahead of Jeff Bryant, who has 689.
Also, Brown has 34 sacks with the Seahawks, putting him seventh all-time in that category, and has three fumble returns for touchdowns, which is tops on the Seahawks' all-time list.
He said his ultimate goal is to make the Seahawks a perennial contender.
"I came here to win and we haven't truly accomplished that yet," Brown said. "I'm not the type of person to just leave something behind just because it didn't work out. I want to keep working at it."
The three-time Pro Bowler finished with 150 tackles in 1998, second-highest single-season total in team history. Terry Beason made 153 in 1978. In his career, he has started 127 of 134 games played, totaling 870 tackles and 64 sacks.
"He's a Pro Bowl player. He's an outstanding football player," said Holmgren. "He's a relatively young man who has a few years left to play at a real high level."