Before the regular season started the Blues were hit hard with an injury to defenseman Erik Johnson. Johnson suffered a leg injury in a golfing accident that put him out for the season. Despite this the Blues had a good start to the regular season, winning their first opening day game in years, and going 5-3-0, before injuries to Manny Legace, Andy McDonald, coupled with poor defensive play, placed the team in last place in their division at 5-8-1. The Blues would win 3 games in a row to make their record 9-8-1. On November 24, 2008, Blues President John Davidson announced the Blues had traded Lee Stempniak to the Toronto Maple Leafs for defenseman Carlo Colaiacovo and center Alexander Steen. On November 30, 2008, Keith Tkachuk became the 6th US-born hockey player and 72nd overall to score 1,000 points in a career. The point came on a goal scored in his 1,077th game. He now has 511 goals and 489 assists. The goal helped the Blues to a 4-2 victory over the Atlanta Thrashers. It was his 362nd point in a Blues' uniform, ranking him eighth all-time. The Blues would lose their next 3 games before winning 4-3 over Phoenix. St. Louis would then lose 3 straight games against teams on the west coast. The Blues would follow up by losing their next two games to extend their losing streak to five. In that period Jay McKee would become another victim of unfortunate injuries for the Blues. The Blues ended the month of December with a poor 4-10-1 record. Just before the All-Star Game break (Jan. 22-28), the team gained seven points in their last four games. On February 6, two days after his 36th birthday, goalie Manny Legace was placed on waivers, and the Blues recalled Chris Holt.
Andy McDonald (C), returned to active status on February 10 after almost three months out with a broken left leg (Nov. 16), and promptly made his presence felt with an assist on the Blues' first goal, and then later added a goal of his own against Vancouver, although they eventually lost.
A 6-2-4 surge in February pushed the Blues (60 pts. on Feb. 24) to an even 26-26 (8 ties) record, and to within five points of the 8th and last playoff spot.
In a dramatic and wild 3-1 win, with the final two goals from the youngsters T.J. Oshie and Patrik Berglund late in the wide-open third period plus 41 saves from Chris Mason (with the help of four Stars' shots off the goal posts plus another one off the crossbar) at Dallas on Feb. 26, pushed the Blues into 12th place in the Western Conference, only three points from a playoff spot and over .500 for the first time since December 8.
A big 6-1 run from Mar. 20 - Apr. 2 pushed the Blues into an 8th place ranking—and playoff contention with the last playoff spot, just behind the 7th place Anaheim Ducks, with a stunning 5-4 win April 2 at Detroit; their first win over them all season, highlighted by David Backes' career-high four-goal night. It was the first four-goal night by any Blues' player since Scott Mellanby did it on March 6, 2003.
A key player in the team's late-season surge has been the exciting play and desperately-needed team offense because of numerous injuries by rookie—and increasingly fan favorite T.J. Oshie, who was named NHL Rookie of the Month for March (Apr. 2) after earning 13 points (4 G, 9 A) in 14 games, with the Blues going 9-4-1 in the month. From Jan. 1 through the game on March 29, Oshie has earned 11 goals and 20 assists for 31 points in those 37 games, leading all rookies but one (Bobby Ryan of Anaheim) in that span. Garnering praise from veterans on the Blues are increasingly common, such as this one from goalie Chris Mason: "T.J. is such a tenacious player. In every game he seems to create scoring chances out of nothing." Oshie was also listed #8 on "Hockey's Future Top 50 prospects." 
The Blues clinched a playoff spot in their second-to-last game of the season (#81), and last home game on April 10, in front of a raucous, standing-room-only crowd of 19,250, beating the Columbus Blue Jackets, 3-1, in their 40th win of the season. The defense was superb, giving up only 17 shots—their lowest of the season. This is the first season since 2003–04 the Blues have made the playoffs. In the 2005-06 season (first year after the lockout year in 2004-05), the Blues were in last place overall, and in 2007-08 they were tied for the fourth-worst record in the NHL. The Blues completed one of the greatest late-season playoff surges in NHL history.
The St. Louis Blues are returning to the NHL Playoffs for the first time since 2004 with a 6th-place finish. They were swept in four straight in the first round by the Vancouver Canucks due to a hot goaltender, Roberto Luongo. It was the first time the Blues were swept in a playoff series since the Dallas Stars did it to them in 1994
2009 Stanley Cup playoffs
Western Conference quarter-final vs. (3) Vancouver Canucks: Vancouver won 4–0
Note: GP = Games Played; TOI = Time On Ice (minutes); W = Wins; L = Losses; OT = Overtime Losses; GA = Goals Against; GAA= Goals Against Average; SA= Shots Against; SV= Saves; Sv% = Save Percentage; SO= Shutouts