Calgary (49-23-7) moved eight points ahead of second-place San Jose in the Pacific with three regular-season games remaining for each team. The Flames, who did not qualify for the Stanley Cup Playoffs last season, won a division title for the first time 2005-06.
Calgary will open the playoffs against the second wild card from the West; the Colorado Avalanche hold a one-point lead on the Arizona Coyotes.
"We've had a good year, a good regular season, but we know the work lies ahead in the playoffs," Flames captain Mark Giordano said. "But we won't take this for granted. It's an accomplishment by our team to finish first in the West. It's not an easy thing to do."
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San Jose (44-26-9) will finish second in the Pacific and have home-ice advantage against the third-place Vegas Golden Knights in the Western Conference First Round.
The Sharks, who defeated Vegas 4-3 in overtime on Saturday, are 1-7-1 in their past nine games and had a season-low 15 shots against the Flames.
"We have to set ourselves up for the playoffs and go in with a good feeling," Sharks forward Timo Meier said. "We have to find our game. It's like doing homework and getting ready for the final exams in the playoffs."
Mike Smith made 12 saves for Calgary, which has won eight of its past 11 games.
"Just a great feeling, somewhat of a sense of relief I guess, but also an excitement," Smith said. "This doesn't come around every year. It's hard to get to the very top.
"The Western Conference is a tough conference, and to get to where we are and to it with the guys we've done it with in here says a lot about this group and the resiliency of this group."