A late Matt Derbyshire strike denied Newcastle a deserved draw and piled more misery on manager Kevin Keegan.
New father Derbyshire scored in the 90th minute to deny Newcastle
Michael Owen almost put Newcastle ahead in the first half but pushed his shot wide after rounding Brad Friedel.
The keeper denied Owen twice more after the break tipping the striker's header over and then pushing away his drive.
Rovers were dangerous on the break but Andre Ooijers's volley was saved and Roque Santa Cruz was off target before Derbyshire ran clear to fire home.
Derbyshire's late strike was a killer blow and harsh on Newcastle, who had shown positive, attacking flair throughout the match.
Newcastle drove at the Blackburn defence right from the whistle with wide men James Milner and Damien Duff at the heart of it all.
Within the first five minutes, Milner pulled the ball back for Duff who squeezed his shot just wide of Friedel's post.
Alan Smith latched onto Milner's ball into the box but his header looped over the bar before Milner saw his shot skim wide.
Newcastle skipper Owen ran clear to carve out another chance for Duff, but the Irish winger saw another effort scrambled clear by the Rovers' defence.
Blackburn were not going to lie down under the pressure but equally there was little build-up play from the visitors and their best chances came on the break.
Stephen Warnock's long-range drive was well off-target and Ooijer's shot also skimmed wide.
England midfielder David Bentley almost started something when he sent Santa Cruz through, but his lofted pass to Benni McCarthy was safely collected by Steve Harper, deputising for the injured Shay Given.
Keegan was then left flapping on the sidelines when Owen looked a certainty to score as he collected Joey Barton's pass and rounded Friedel, only for his final shot to skip across the face of the goal.
Blackburn applied some late first-half pressure, but Harper punched away Morten Gamst Pedersen's corner and was alert again to block another Ooijer volley.
Newcastle came out after the break with the same determined attitude but Keegan was left shaking his head again as Milner and Duff's best efforts to break through were thwarted by Rovers' rigid defence.
A moment of rash defending from Stephen Taylor almost let Blackburn in at the other end when Santa Cruz picked up the loose ball, then skied it over the bar.
Harper also made an important block at his near post when Pedersen met Bentley's deep cross with a volley.
As Newcastle drove on, Smith screwed his effort across the goal before Owen was denied twice by Friedel.
Friedel (left) kept a rampant Owen at bay throughout the game
First, Owen headed Nicky Butt's pass but the American keeper tipped the goal-bound shot over. Then Owen's rampaging run came to nothing when Friedel sunk to the grass to push clear his final shot.
The England striker was denied a third time by Blackburn's tenacious defence and Milner saw his tame shot saved by Friedel and another decent effort blocked.
Frustrations boiled over towards the end of the match, when Habib Beye and Morten Gamst Pedersen tussled over who had been awarded a throw-in.
After a mass 'discussion' between both teams, Beye and Pedersen were cautioned but the real drama was still to come.
Following another surge forward by Newcastle, Rovers launched a counter-raid as Bentley unleashed substitute Derbyshire.
The forward ran clear and hit a clean ball beyond Harper in the 90th minute to keep Blackburn's push for Europe on track.
The result leaves Keegan still searching for his first win, and probably wondering just what his team have to do to earn it.
Newcastle boss Kevin Keegan:
"Confidence is low, but we must not allow this to knock us. I feel really sorry for the players.
"They need to know how to win again and they've forgotten what that feels like.
"They must gain something from today because if we play like that we won't have problems. They were magnificent but got caught with the sucker-punch."
Blackburn boss Mark Hughes:
"It was a hard result on Newcastle but our concern is more about what we're doing and our ambition is to get into Europe.
"We are in the mix and back on track. It will be an interesting run up and we just have to do our job now.
"We felt there was something in the game for us and kept going. It was a cool finish from Matt Derbyshire."
Newcastle: Harper, Beye, Taylor, Faye, Jose Enrique, Milner, Barton, Butt (Martins 67), Duff (N'Zogbia 78), Owen, Smith.
Subs Not Used: Forster, Cacapa, Carroll.
Blackburn: Friedel, Ooijer, Samba, Khizanishvili, Warnock, Emerton (Derbyshire 61), Bentley, Reid, Pedersen, Santa Cruz, McCarthy (Roberts 60).
Subs Not Used: Brown, Kerimoglu, Mokoena.
Booked: Bentley, Pedersen.
Goals: Derbyshire 90.
Ref: Rob Styles (Hampshire).
BBC Sport Player Rater man of the match: Roque Santa Cruz 7.65 (on 90 minutes).
Please note that you can still give the players marks out of 10 on BBC Sport's Player Rater after the match has finished.