Earlier this summer, the Baggies had activated a 12-month option on the 29-year-old midfielder's previous contract, but he has now agreed improved terms until 2017.
Albion head coach Alan Irvine said: "I'm delighted we have extended Chris' contract by a further two years.
"He's our captain, has great quality and experience and is clearly a very, very important player for us.
"Chris is an influential figure both on and off the pitch. He has the respect of all the players and staff and is a top class professional."
Brunt, who moved to the Hawthorns in August 2007, is one match away from his 250th competitive appearance for the club.
He took over the captaincy during the 2010/11 season, and earlier this week Irvine had confirmed he would retain it for the coming season, meaning he had served as skipper for four different managers - Roy Hodgson, Steve Clarke, Pepe Mel and Irvine.
Brunt joins England goalkeeper Ben Foster in signing a new deal after a busy summer which has already seen Craig Gardner, Joleon Lescott, Chris Baird, Brown Ideye, Cristian Gamboa, Jason Davidson, Sebastien Pocognoli and Andre Wisdom join the Baggies.
- Sports & Recreation
- Alan Irvine