Patrik Berglund and David Backes scored goals 1 win over the Anaheim Ducks.
The Blues moved to 7-1 in their last eight games for an NHL-best 93 points -- two more than the Eastern Conference-leading New York Rangers.
They took a four-point lead over idle Detroit for first place in the Central Division.
"We're absolutely having fun," said Backes. "You're winning hockey games and you're coming to the rink and having success for the work you're putting in and that's what it's about is getting rewards for the efforts and for committing to that all for one type of goal."
Backes also scored the first goal for the Blues, who rattled off three unanswered after falling behind early in the second period. Jaroslav Halak made 24 saves in the win.
Corey Perry scored for Anaheim and Jonas Hiller gave up three goals on 27 shots. The Ducks have lost four of their last six.
Andy McDonald, a former Duck, set up Berglund's go-ahead goal at 4:47 of the third period with a pass from behind the end line that found his teammate in front for a tap-in on the right side.
Backes' second power play goal of the night -- he was in the slot to get a piece of Kevin Shattenkirk's slap shot from the point -- gave the Blues their 3-1 lead at 6:48.
Anaheim went 0-for-3 on the power play.
"We're not working as a unit as much as we need to and it's tough," said Ducks forward Ryan Getzlaf. "We're doing a couple of different things than we're used to doing and we're not responding the way we need to."
Earlier, Hiller got nine saves and Halak had five in a scoreless first period. Perry gave the Ducks a 1-0 lead 4:18 into the second on a wrister from the right side, but Backes tied it at 11:38 with a tip-in on the power play.
The Blues, who beat Chicago on Tuesday, are 13-4 in their last 17 games and 2-0 on a three-game homestand that ends Saturday in Columbus with the opener of a home-and-home against the Blue Jackets.
Sunday's game at Columbus starts a seven-game road trip for the Blues, who will actually play nine of their last 13 games of the season on the road.
The Ducks started a three-game road trip that continues on Saturday at Dallas...The Blues were 2-for-4 on the power play.