ALBION were denied all three points in the cruellest of fashion as Cardiff levelled a dramatic contest with virtually the last kick of the game.
Thievy Bifouma looked to have secured a crucial victory when he converted Saido Berahino's left-wing cross in the fourth minute of injury time.
But fellow substitute Mats Daehli popped up a minute later at the other end to level for the Bluebirds courtesy of a deflected effort - denying Pepe Mel his first Hawthorns victory and ensuring the shares were spoiled after a thrilling contest.
The Baggies stormed out of the blocks and surged in front inside two minutes thanks to Morgan Amalfitano’s stunning 35-yard lob – his third goal of the campaign.
It got even better for Mel’s men in the ninth minute when Graham Dorrans stabbed home his first goal in a year.
Albion dominated the first half but were only a goal to the good at the break after Jordon Mutch beat former fellow Blues player Ben Foster with a sublime long-range chip in the 30th minute.
The Baggies had chances to extend their lead after the break but in a more even half, City levelled 17 minutes from time thanks to Steven Caulker’s looping header.
Sixteenth entertained 19th, with the two teams separated by just three points, in this crucial basement battle.
Mel made two changes as Matej Vydra and fit-again Amalfitano came in for the injured Victor Anichebe (hamstring) and Thievy, who was joined on the bench by Academy graduates Liam O’Neil and Kemar Roofe.
The Hawthorns was absolutely rocking at kick-off – and the volume was pumped up even higher with less than two minutes on the clock.
Foster’s huge clearance was unwittingly headed on by Gary Medel and Amalfitano beat David Marshall all ends up with the most audacious of angled lobs from 35 yards. It was right up there with his sensational solo strike at Manchester United as a goal-of-the-season contender.
It was the first time Albion had taken the lead at home under head coach Mel – and the early breakthrough injected renewed belief into the hosts.
They hunted Cardiff’s players all over the park and Marshall had to pull off a fine save in the fifth minute to keep out James Morrison’s 15-yard volley, after he had ghosted onto fellow Scotland international Dorrans’ lofted pass.
But Albion weren’t to be denied a second goal much longer. Four minutes later, Amalfitano’s angled ball into the box was tapped neatly across goal by Vydra and Dorrans stabbed home from eight yards.
Cardiff looked shell-shocked and barely made it into the Albion half until the 19th minute, when they attacked down the left. Andrew Taylor’s low cross was nudged away from the lurking Fraizer Campbell by Steven Reid’s outstretched boot and Foster gathered.
Just three minutes later, Albion threatened again. Following Stephane Sessegnon’s purposeful run down the left, Liam Ridgewell’s low cross found Vydra whose shot was blocked in a crowded goalmouth.
Albion looked completely in control but, out of the blue, had their two-goal cushion halved on the half-hour mark.
In almost a carbon copy of Amalfitano’s opener, Mutch directed a 35-yard chip from the right over Foster’s despairing dive and into the far top corner. The goal gave City renewed hope but they still struggled to create chances and Ole Gunnar Solksjaer made a change on 36, replacing Fabio with on-loan Manchester United man Wilfried Zaha.
Albion regrouped and Youssouf Mulumbu’s 30-yard grass-cutter caused Marshall more problems than it should have, with the Bluebirds No.1 having to gather at the second attempt.
City’s only other effort of the half came on 42, when Medel screwed a 20-yarder well wide from Aron Gunnarson’s lay-off.
But the Baggies finished a half they had dominated on the front foot, with the lively Dorrans curling a 20-yard free-kick over the bar and into the Smethwick End.
In another first for Mel, Albion headed into the interval ahead for the first time during his ten-game reign.
Solksjaer made another change at the break, replacing Gunnarson with Daehli.
Backed by a wall of noise from the home hordes, Albion made a bright start to the second period and Craig Dawson wasted a half-chance to test Marshall when he hacked over Gareth McAuley’s nod down from Vydra’s centre.
Then, on 50, Mulumbu’s goalbound effort was unwittingly diverted just wide by the frame of Dawson.
Albion were turning the screw and should have been further ahead on 52. After Marshall had come off his line to block at the feet of Vydra from Sessegnon’s through-pass, the ball fell invitingly for Morrison who could only smash high into the Brummie Road End from 12 yards.
Cardiff did not threaten again until the 54th minute, when stand-in skipper McAuley’s error let in Craig Bellamy. However, Dawson came to his central-defensive partner’s rescue with a wonderfully-timed tackle.
The game was becoming incredibly stretched and after a fine Baggies breakaway, Dorrans saw a 20-yard piledriver blocked by Caulker. Moments later, Amalfitano just failed to get a touch on Ridgewell’s sublime ball across the six-yard box.
Foster was called into action for the first time in a long while on 63 when he pushed wide Campbell’s swirling 25-yard shot.
Cardiff were now enjoying much more possession but struggled to get any change out of the Baggies rearguard.
Mel made his first change on 71, replacing the tiring Amalfitano with Saido Berahino.
But disaster struck on 73. From Medel’s floated free-kick into the Baggies box, Caulker rose highest to direct a superb looping header inside the far post.
It was a bitter pill to swallow and Dawson was unable to keep his header on target from Ridgewell’s lofted free-kick into the City box.
The encounter looked set to finish level at 2-2 but, in the fourth minute of injury time, Thievy poked home from close range to leave Cardiff's players on their knees.
Yet it was the visitors who had the final say as Daehli converted from ten yards via a deflection among a host of bodies.
ALBION (4-3-3): Foster; Reid, McAuley (c), Dawson, Ridgewell; Morrison, Mulumbu, Dorrans (Gera 85); Amalfitano (Berahino 71), Vydra (Thievy 78), Sessegnon. Subs not used: Myhill (gk), Lugano, O'Neil, Roofe.
CARDIFF (3-5-2): Marshall; Theophile-Catherine, Caulker (c), Turner; Fabio (Zaha 36), Medel (Whittingham 88), Mutch, Gunnarsson (Daehli HT), Taylor; Bellamy, Campbell. Subs not used: Lewis (gk), Jones, Cowie, Cala.
GOALS: ALBION – Amalfitano (2), Dorrans (9), Thievy (90+4). CARDIFF – Mutch (30), Caulker (73), Daehli (90+5).
BOOKINGS: ALBION – Dorrans (foul 64).
REFEREE: M Oliver (Northumberland).
ALBION STARMAN: Graham Dorrans.