Inspired by the radar-like boot of Morne Steyn, who kicked four dropped goals in a 21-point haul, the Bulls ensured favouritism for next weekend's final as the Chiefs face a daunting Loftus Versfeld assignment as last New Zealand team standing.
The Crusaders dominated the opening quarter but had no answer to a Bulls rampage either side of halftime, with dynamic No 8 Pierre Spies an influential figure.
The Bulls scored three tries to two to repeat their semifinal victory of two years ago against the Crusaders at Loftus, which was followed by their only Super 14 title. Next weekend will be their first home final.
Playing before a screaming full house of 52,000, the victory extended the Bulls' winning streak to 10 matches at their home fortress.
It ended an impressive season by the Crusaders under new coach Todd Blackadder and without several 2008 stars including Dan Carter and Ali Williams, as they scraped into the playoffs fourth on points differential.
"We felt like we had the momentum and that 10-minute patch just before halftime gave it back to the Bulls. They went into halftime with their tails up and we were perhaps a little bit shellshocked," captain Richie McCaw told Super Sport.
"But I'm proud of the way the guys stuck at it right to the end. It's been a hell of a season to get here."
The Crusaders arrived confident of their fifth win at Loftus, and won the pre-match joust with lock Brad Thorn (hamstring) and Andy Ellis (ribs) passed fit, while the Bulls lost Springboks centre Wynand Olivier (hip) and fellow midfielder JP Nel (suspended).
They began magnificently, and an eerie silence descended upon Loftus when they raced to a 20-7 lead inside 25 minutes.
With their scrum and lineout asserting early dominance, and brutal contact in the tackle forcing Bulls errors, the Crusaders were at their clinical best.
After Bulls flyer Bryan Habana dashed 30m untouched to score the first try, the visitors stormed back with two tries in 10 minutes.
Winger Adam Whitelock crossed out wide from quick hands down the blindside, then flanker Kieran Read towered above fullback Zane Kirchner from a pinpoint Stephen Brett bomb to score beside the posts.
But someone flicked a switch and the Bulls roared in for 20 points in the final eight minutes of a remarkable first half.
Halfback Fourie du Preez worked the blindside to send winger Akona Ndungane away, then the Crusaders suffered a blow five minutes before the break when No 8 Thomas Waldrom was sinbinned by referee Bryce Lawrence for a professional foul.
Steyn snapped two dropped goals in two minutes then the Bulls punished a poor Jared Payne chip kick when Spies dashed 65m to score on the stroke of halftime.
Waldrom returned and so did the Crusaders' composure, with 10 phases of attack ending with Ellis snapping a dropped goal, narrowing the gap to four.
Centre Jaco Pretorius thought he'd put the Bulls further ahead on the 60 minute mark but Lawrence called him back for a clear forward pass.
Inevitably it was Steyn's boot which gave the Bulls breathing space. He goaled his first penalty in the 67th minute when Thorn was ruled to have pulled down Victor Matfield at a lineout, then nailed two more dropped goals in two minutes to build a decisive buffer.
