The Blues have dislodged the Hurricanes from atop the Super Rugby Pacific table for the first time this season, edging their rivals from capital 31-27 at Auckland's Eden Park.
Each team scored four tries, but the faultless goalkicking of first-five Harry Plummer proved decisive for the home side, who defended grimly in the final moments to hold their opponents out at the death.
The Hurricanes suffered their first loss of the season only two weeks ago, but their second will see them slip to second on the ladder, with three rounds remaining in the regular season.
The Hurricanes were hit by late changes, when centre Bill Proctor, lock Caleb Delany and prop Tyrel Lomax were all scratched, severely testing their depth. Bailyn Sullivan, Justin Sangster and Pasilio Tosi were all promoted to the starting XV.
From the kickoff, the Blues surged into the 22 and were initially ruled to have been held up over the line, then grounded for a try, but eventually disallowed for a double movement. From an attacking lineout, hooker Ricky Riccitelli was stopped short, but centre Bryce Heem plucked the ball from the ruck to score.
With their first opportunity, Hurricanes second-five Jordie Barrett kicked from his own half to touch metres out from the corner flag and captain Brad Shields was driven over from close range.
They went close again, when Sullivan busted through the midfield defence and winger Josh Moorby dived at the corner flag, but was denied by counterpart Caleb Clarke. Seconds later, Plummer dragged fullback Ruben Love out in the other corner.
As the Blues tried to break out of their half, fullback Zarn Sullivan - in his first game back from knee injury - went down with no-one around him and had to be carted off the field, much to the concern of brother Bailyn.
The Hurricanes threatened to score again, but when they turned the ball over near the tryline, Clarke busted out of the 22 and No.8 Hoskins Sotutu surged over halfway. The Blues' progress was stalled, when flanker Akira Ioane was yellow-carded for a high cleanout at the ruck.
Plummer put Heem through space and upfield. Two close-range penalties in succession turned to lineouts that came to nothing, before a third finally saw replacement fullback Cole Forbes score.
When Ioane returned just before halftime, his team had actually stretched their advantage in his absence, but with time up, the Hurricanes struck, when Moorby couldn't be denied again.
Ahead 14-10 at the break, the Blues kept the ball in hand from the restart, but could not convert that possession into points.
Instead, flanker Peter Lakai scored at the other end to put the visitors ahead for the first time, with Barrett taking over kicking duties from wayward Brett Cameron.
Back came the Blues, after a penalty kick to the corner and a lineout maul, with the ball released for winger Mark Tele'a to score next to the flag. Plummer continued his faultless goalkicking display with a sideline conversion.
Barret reduced the deficit to a point with a penalty, but another attacking lineout set the platform for replacement prop Angus Ta'avao to score for the Blues, with Plummer's fourth conversion extending the margin beyond a converted try.
Hurricanes halfback TJ Perenara brought his team back into the contest, darting over from a lineout maul and adding another to his Super Rugby tryscoring record. With 10 minutes remaining, the margin was back to one.
Plummer chipped over a penalty to create some breathing space for the home side, but with time running out, the Hurricanes had their chance to steal victory with an attacking penalty that they kicked to the corner.
At the lineout, the Blues forwards held up the maul and the ball was released. Another penalty was tapped, but replacement halfback Sam Nock stole the ball and kicked dead to end the contest.
"Those are the games you want to be a part of," reflected Blues captain Patrick Tuipulotu. "We often put a measurement on defence and in tough times like that, that's when it counts.
"We want to back our 'D' and trust it, and it's good to see it paid off in the end.
"It's very big - it was a test match for us and with a couple more games before finals, it puts us in good stead."
The Blues next host the Highlanders next Saturday, while the Hurricanes will want to bounce back at home against Moana Pasifika on Friday.
Blues 31 (Heem, Forbes, Tela'a, Ta'avao try; Plummer 4 conversions & penalty) Hurricanes 27 (Shields, Moorby, Lakai, Perenara try; Barrett 2 conversions & penalty)
