Brisbane led by 46 points at the final break but conceded five straight goals to create some anxious moments in an eventually relieving 11.21 (87) to 10.7 (67) victory.
The Lions had given away big leads to lose their past two games and the wounds suddenly opened when the Bombers, buoyed by a fine farewell display by Dyson Heppell, got within 19 points with eight minutes still to play.
But they held on this time, last year's defeated grand finalists to play eighth - any of Carlton, Fremantle or the Western Bulldogs - at the Gabba in week one of the finals after being 13th after 12 rounds.
Brisbane rising star Will Ashcroft had a field day in the Lions' comfortable win. (Darren England/AAP PHOTOS)
"We were a long way in front but it's more the frustration of having 32 shots on goal and four out on the full as well," he said.
"The game shouldn't have been as close as it was and this is what we've done for the last three weeks and I'm just hopeful we got it out of our system."
Charlie Cameron showed glimpses of his best in a three-goal haul, his biggest since he kicked five in a round-11 mauling of Richmond and just the third time he's kicked three or more majors all season.
The livewire had kicked at least 54 goals in the past four seasons of regular length and game time, but boasts just 37 this year.
Cameron's dare and confidence were back in the first half, backing himself with a long-range snap and also setting up Logan Morris with an lasered cross in the second quarter and providing several clever handballs.
Inaccuracy and wastefulness in front of goal almost cost them again, but the Bombers were their own worst enemies, battling to exit their back half as opportunities fell into the laps of waiting Lions forwards.
The retiring Heppell (34 disposals) was immense in his farewell appearance, Jake Stringer (two goals) kissing the logo on his chest devoted to the former captain when he launched a trademark goal from deep on the boundary line.
Retiring Essendon veteran Heppell kept the pressure right on Brisbane's Logan Morris. (Darren England/AAP PHOTOS)
Kyle Langford kicked three goals for the Bombers, while Zach Merrett (37 touches, one goal) and Andrew McGrath (34 disposals) did the heavy lifting for Brad Scott's side.
With six losses from their last seven games Essendon slid out of the top four and will miss the finals.
"The end of the game was really pleasing. outplayed clearly for the first three quarters," he said.
"Very difficult, psychologically, when your season is done ... but is does lay a platform for the future and tells you a bit of a story about your players."
Joe Daniher had his moments in game 200, bombing a goal from 60m on the run shortly after missing a closer set shot.
A brilliant effort produced a wry smile from the former Bomber, only for it to be denied after a lengthy review deemed his shot had shaved the post.
The key forward, much to the full Gabba house's dismay, also had two clear marks in the goal square not paid by officials.
Kai Lohmann (three goals) was electric early, while Dayne Zorko and Josh Dunkley got plenty of ball and Lachie Neale (40 touches, one goal) was his usually prolific self.
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