Blues held off a Western Force revival to claim a 31-21 victory on Saturday and confirm they will host the Highlanders in an all-New Zealand Super Rugby Trans-Tasman final next weekend.
Hoskins Sotutu scored two of the Blues tries as they raced to a 28-0 lead at halftime, only to be denied a bonus point when the Force came to life with three second-half tries.
In a cliffhanger final round of the regular season, with the top two teams going directly into the final, the Blues, Highlanders and Crusaders all finished unbeaten and equal on bonus points, leaving the finalists to be decided by points differential.
The Blues came out on top with a margin of 119, heading the Highlanders on 103 with the Crusaders on 97.
After the Highlanders' 33-12 win over the Brumbies on Friday, the Crusaders needed to beat the Melbourne Rebels on Saturday by 32 points and fell just short with a 52-26 scoreline in Sydney.
While the Crusaders were left to rue several missed opportunities, the Blues made the most of every scoring opportunity in the first half only to fall off the pace after the turn.
Captain Patrick Tuipulotu admitted that was not a good sign going into the final.
"It's fair to say we did not turn up in the second half," Tuipulotu said.
"A perfect 40 is never good enough. We're always striving for a perfect game, for a perfect 80.
"Against the Highlanders, we know they're a dangerous team and they go 80 plus as well."
Sotutu scored the opening try in the 10th minute when a clearing kick by TJ Faiane was regathered by the Blues.
Hulking wing Mark Talea proved impossible for the second before Dalton Papalii crashed over from close range and Sotutu made light of the defence for his second.
Otere Black converted all four for the Blues to turn with a commanding lead.
But a Black penalty was all the Blues could manage in the second half while the Force produced tries to Feleti Kaitu'u, Tevita Kuridrani and Rob Kearney all converted by Ian Prior.
Despite a Sevu Reece hat-trick, the Crusaders fell one converted try short in a pulsating clash against the winless Rebels at the Leichhardt Oval – a game moved to Sydney due to a recent Covid-19 outbreak in Melbourne.
The Crusaders attacked relentlessly from the start in sunny conditions and eased the pressure on themselves with early tries to Mitchell Drummond and a hard-running Will Jordan.
The Rebels impressively were able to resist the assault from the Crusaders, whose nerves were heightened when Braydon Ennor inexplicably fumbled the ball running unopposed to the line just before halftime.
A try from Frank Lomani and subsequent conversion from Carter Gordon reduced the Crusaders' lead to only 12 points with 15 minutes remaining.
In a late flurry they managed further tries to Oli Jager and Braydon Ennor before running out of time.