Jackman, 26, was a 1999 first-round draft pick of the Blues and was due to become a free agent after the season. This season he has two goals and six assists in 58 games, along with 63 penalty minutes, and is second on the team in ice time, averaging 21:57 per game.
"Barret has been a staple on the blue line for the Blues since his rookie season," team president John Davidson said. "He logs plenty of minutes per game and will continue to be a key part of our team as we move forward."
The Blues are 12th in the Western Conference and six points out of the final playoff spot with a record of 28-24-10 and 66 points. The contract extension perhaps indicates a decision not to shed talent at the deadline.
Davidson said the franchise has a bit of a balancing act. The Blues have missed the playoffs the last two years while rebuilding under new ownership but have won back much of their fan base with a competitive roster featuring free agent pickup Paul Kariya, goalie Manny Legace and 32-goal scorer Brad Boyes.
"We'd certainly love to make the playoffs, but we're also trying to do what's right long-term for the team," Davidson said.
Davidson said he's had a number of discussions with other franchises, none of them serious.
"There's a lot of people kicking tires today," Davidson said. "It's like everybody's on the driving range, but there's not too many people on the tee box."
Jackman has played in 289 career NHL games in six seasons, all with the Blues. He was the first Blues player to capture the Calder Trophy as the league's most outstanding rookie in 2002-03.
"I have said all along that I wanted to remain in St. Louis," Jackman said. "The Blues drafted me, I met my wife here and I want to raise a family here.
"I'm excited about the direction of this franchise and love playing in front of Blues fans."