The 29-year-old Howard is in his fourth season as the Red Wings' top goalie.
"We're extremely pleased to have Jimmy under contract for the next six seasons,'' general manager Ken Holland said. "He's entering the prime of his career and over the last four years has gained a tremendous amount of regular season and postseason experience.''
Howard is 17-12-6 with a 2.31 goals-against average and a .920 save percentage this season. Detroit is in a wild race for the final playoff spots in the Western Conference, hoping to extend their postseason streak to 22 years.
Howard was drafted by Detroit in the second round in 2003. In 2009-10, he went 37-15-10 with a 2.26 GAA, becoming the fourth goalie in team history to win at least 30 games as a rookie.
He went on to become the first Detroit goalie to win at least 35 games in each of his first three full seasons.
"He's developed into a top-tier NHL goaltender and is a very important part of our team moving forward,'' Holland said. "Jimmy is one of our leaders and we look forward to watching him elevate his game to the next level in a Red Wings' sweater.''
After Monday's games, Detroit was tied for eighth in the West with Columbus, although the Red Wings have played one fewer game. Dallas was two points behind the Red Wings and Blue Jackets, with Phoenix another two back.
Howard's 2.38 GAA over the last four seasons ranks him 11th in the league in that span. What he has yet to do is lead the Red Wings on an extended postseason run. He's 13-15 with a 2.63 GAA in the playoffs, and Detroit hasn't made it past the second round since 2009.