PETER Odemwingie's stunning 89th-minute strike earned Albion their first-ever Barclays Premier League win at Ewood Park.
The Nigeria striker beat Paul Robinson all ends up with a 20-yard rocket - his third goal of the season and first in two months.
James Morrison had put the Baggies ahead with an effort of equal quality, breaking the deadlock with a 25-yard volley in the 52nd-minute.
The first-half had been even-stevens but Albion took complete control after their opener, with Ben Foster untroubled.
But Rovers snatched an equaliser out of the blue when Scott Dann, a summer signing from Blues, bundled home his first goal for the club in the 72nd minute.
However, the Baggies were not to be denied a third, and fully deserved, away win of the term.
There was plenty at stake at Ewood Park as 19th entertained 15th, with the two teams separated by just five points.
Paul Scharner was handed his first start in seven games in Roy Hodgson's only change. Jerome Thomas made way. Steven Reid passed a late fitness test on a knee injury to line up against his former club while Gabriel Tamas replaced Somen Tchoyi on the bench.
Steve Kean made two enforced changes as Steven Nzonzi and Ruben Rochina came in for injured duo Michel Salgado and Gael Givet. Former Baggies striker Jason Roberts was on the bench.
The game took a while to settle down but Albion enjoyed plenty of possession in the Rovers half during the opening stages and it was no surprise to see them create the first half-chance.
Morrison, pushed into a wide-right role following Scharner's recall to central midfield, found Odemwingie in space on the left in the fifth minute and the striker cut into the box before blasting wide from a tight angle.
Blackburn had barely got out of their own half as the game passed the ten-minute mark and Dann came to Rovers' rescue when he blocked Morrison's goalbound effort after Odemwingie had helped on a Chris Brunt free-kick.
Albion kept pressing and created the first clear-cut opening on 15 when Nicky Shorey threaded in Brunt down the left. The skipper found Odemwingie unmarked at the near-post but his flicked header flew wide of the far post.
Blackburn stemmed the one-way traffic when Jason Lowe cut inside Shorey on the Rovers right before seeing his miscued shot reach Yakubu in the box, but Foster raced off his line to smother the ball.
The action immediately swung to the other end and Robinson was relieved to see the ball creep wide of his left-hand post after spilling an awkward 20-yard drive from Odemwingie.
A Reid slip then allowed Blackburn to break down the left and Rochina did well to carry the ball into a crowded Baggies box before seeing his goalbound effort blocked by Scharner.
The hosts were enjoying their best spell of the game and it took a last-ditch challenge from Scharner to prevent Mauro Formica firing at Foster's goal following Rochina's foraging run.
The game descended into a scrappy passage of play and it wasn't until the 38th minute that either team mustered a shot at goal, with Foster doing well to push over a ferocious Morten Gamst Pedersen free-kick.
Albion were getting into plenty of promising positions but their final ball lacked quality. However, they almost snatched a 41st-minute lead when Brunt got his delivery spot on. With his back to goal, Long flicked it on from eight yards, only to see his header fly just over.
Blackburn were next to threaten when Yakubu found David Dunn just inside the box but Reid denied his former team-mate a clear sight of goal with a last-ditch interception.
In stoppage time, Long slipped in Odemwingie down the right and had the striker squared to Scharner in the box, the Austrian would have been in on goal, but the former Lille striker's pass slid behind his team-mate.
It was Blackburn who launched the first attack of the second half but Steven Nzonzi failed to trouble Foster's goal with a tame 25-yard shot.
But Albion came within a whisker of breaking the deadlock on 50.
Youssouf Mulumbu found Morrison with a diagonal ball and from his pull-back, Scharner saw a 15-yard shot creep past Robinson but also the far post.
Albion were getting on top and Chris Samba did well to divert Long's drive wide for a corner.
But the Baggies drew first blood from Brunt's ensuing flag-kick.
Nzonzi's clearance looped straight to Morrison 25 yards out and the Scotland star beat Robinson all ends up with a stunning first-time volley.
Albion went hunting a second goal and only Pedersen's far-post clearance denied Long a simple headed chance from Brunt's far-post centre.
And, on 64, Dann almost gifted the Baggies a two-goal cushion when, in dispossessing Long just inside the Blackburn half, he unwittingly lofted the ball back towards his own goal, over Robinson and, to his great relief, just wide of the left-hand post.
The Baggies were certainly not sitting on their advantage and Foster's goal remained untroubled as the clock passed the 70-minute mark.
However, totally against the run of play, Rovers were level on 72 with a real 'route one' effort.
Robinson launched a free-kick high into the Albion penalty area and Samba towered above Gareth McAuley to head across the face of goal to central-defensive partner Dann, who bundled the ball past former Blues team-mate Foster from close range.
Albion got back on top during the final stages, putting the Rovers goal under considerable pressure.
Robinson managed to steal the ball off Long's toes in an almighty goalmouth scramble and, on 80, Odemwingie cut across the penalty area before dragging his shot wide of the right-hand post.
However, Blackburn were also pushing for a winner and, either side of a Morrison 25-yarder which fizzed over, Samba headed straight at Foster from Lowe's hanging cross and David Goodwillie shot tamely at the Albion No.1 from fellow sub Roberts' lay-off.
Morrison had a taste for the spectacular and, three minutes from time, he saw Robinson palm away another 25-yard cracker.
A minute later, Foster also had an awkward shot to deal with but managed to collect Nzonzi's swirling long-range drive at the second attempt.
Moments later, Foster had little trouble holding onto Yakubu's angled shot from Roberts' tee up.
But Albion had been on top for long periods of the second 45 and they got their noses back in front in the penultimate minute.
There was little on when Odemwingie collected the ball wide on the right but after skipping past Goodwillie and Pedersen, he directed an unstoppable curler from just outside the box into the far corner of Robinson's net.
It was a strike to rival Morrison's for the goal-of-the-season gong and good enough to grace any game.
There was still some work to be done and Albion had to defend a late aerial barrage, which they did manfully.
Roberts had a shot deflected wide before Reid denied Goodwillie what looked a certain equaliser by blocking his snapshot inside the box.
The terrific away support had made themselves heard all afternoon but saved their biggest cheer for Mark Clattenburg's full-time whistle.
BLACKBURN (4-4-2): Robinson; Lowe, Samba, Dann, Pedersen; Rochina (Goodwillie 79), Nzonzi, Dunn (Hanley 62), Vukcevic (Roberts 62); Formica, Yakubu. Subs not used: Bunn (gk), Petrovic, Blackman, Henley.
ALBION (4-4-2): Foster; Reid, McAuley, Olsson, Shorey; Morrison (Thomas 89), Scharner (Dorrans 81), Mulumbu, Brunt; Long, Odemwingie (Dawson 90+2). Subs not used: Fulop (gk), Jones, Tamas, Cox.
GOALS: BLACKBURN - Dann (72). ALBION - Morrison (52), Odemwingie (89).
BOOKINGS: BLACKBURN - Pedersen (foul 77). ALBION - Scharner (foul 37).
REFEREE: M Clattenburg (Tyne & Wear).
ALBION STARMAN: James Morrison.