GOALS in each half from Chris Burke and Peter Whittingham ended below-par Albion's six-match unbeaten run and secured Cardiff's first league win at The Hawthorns in almost 53 years.
The hosts suffered what could only be described as a bad day at the office and fell behind in the 18th minute when Burke was allowed to advance forward and fire home from 25 yards.
The Baggies spent the rest of the game trying to breach the Bluebirds' resolute rearguard but the game was effectively up when captain Scott Carson was red carded for violent conduct eight minutes from time.
In a double blow, the keeper's offence presented City with a penalty and Whittingham made it 2-0 from the rebound after seeing his spot-kick saved by sub keeper Dean Kiely.
Roberto Di Matteo, without six first-team regulars, made two changes to his starting XI, with Roman Bednar replacing the injured Luke Moore and Youssouf Mulumbu coming in for Joe Mattock, who dropped to the bench.
Second-placed Albion started the day eight points and three positions better off than Cardiff, who also made two changes. Rae and Kelvin Etuhu came in for Jay Bothroyd (suspension) and Joe Ledley (groin).
Graham Dorrans had been moved from his usual central midfield position out to the left wing - and it took him less than two minutes to shine in his new role.
The Scotland international cut inside former Baggie Riccardo Scimeca before unleashing a 25-yard drive which David Marshall did well to turn around his near post.
Dorrans took the ensuing corner, which Cardiff only half cleared, but Gonzalo Jara was well off target with a 25-yard volley.
City recorded their first effort at goal in the ninth minute when Whittingham's free-kick fell neatly for Etuhu in the box, only for the striker to fire over on the turn.
That effort sparked a mini spell of City pressure and Burke went much closer with a 20-yard drive which fizzed just over after exchanging a short corner with Michael Chopra.
Albion were soon back on the attack and the in-form Dorrans set up an opportunity for Bednar after leaving full-back Paul Quinn for dead down the left.
Bednar controlled Dorrans' cross in the box but Marshall was alert and rushed out to block the Czech international's shot at point-blank range.
In what was proving a lively opening, Carson had to pull off an even better save in the 14th minute when his finger-tips diverted Rae's 20-yard snapshot over from Gianni Zuiverloon's headed clearance.
Cardiff are only behind Albion in the Coca-Cola Championship scoring charts and carried a real threat every time they attacked.
Etuhu will feel he should have done better with a header from Burke's cross - before the visitors broke the deadlock on 18.
Burke broke unchallenged from just inside the centre-circle before planting an unstoppable 25-yard drive inside Carson's right-hand post.
Albion regrouped but severely lacked fluency.
Cardiff also made life difficult by getting plenty of men behind the ball and playing on the break.
And from one such counter-attack, Carson had to be alert to push wide Whittingham's acute header from the impressive Burke's centre.
Albion's lack of cohesion prompted Di Matteo to ring an early change, with Mulumbu, who had earlier needed lengthy treatment on a knee injury, being replaced by Filipe Teixeira in the 36th minute.
The switch almost paid dividends as a move involving Dorrans, who had reverted back to the midfield engine room, resulted in Marek Cech firing just wide from 20 yards.
But that proved the final action of a disappointing half for the hosts.
Albion made a much brighter start to the second 45 and Marshall had to pull off a goal-saving block on 49 to deny Bednar, who had been put clear by the lively Simon Cox's superb ball.
The Baggies, who were keeping Cardiff penned inside their own half, went even closer six minutes later when Quinn slid in on Bednar, only to divert the ball into Dorrans' path.
The former Livingston ace advanced into the box before screwing his shot just wide of the far post.
But Albion soon reverted to their bad habits of the first half as the game continued to be a pale shadow of Saturday's thrilling contest at Pride Park.
Time after time, Baggies moves broke down on the edge of the Bluebirds' box and when Brunt and Cech tried their luck from distance, they were both well off target.
However, a moment of magic from Brunt in the 68th minute almost fashioned a leveller.
The Northern Ireland international seized on a wayward City pass and advanced to the edge of the penalty area before firing inches wide of the right-hand post, with Marshall beaten.
A decent chance went begging five minutes later when Bednar failed to make proper contact with a free header from Zuiverloon's diagonal centre.
Albion's night went from bad to worse eight minutes from time when skipper Carson was red-carded for violent conduct after clashing with Chopra in the box and referee Paul Taylor pointed to the spot.
With Cech being sacrificed, Kiely took over between the sticks and saved Whittingham's spot-kick, only for the ball to rebound straight back to the ex-Villa man to slot home.
ALBION (4-4-2): Carson; Zuiverloon, Meite, Olsson, Cech (Kiely 83); Brunt, Mulumbu (Teixeira 36), Jara, Dorrans; Bednar, Cox. Subs not used: Martis, Wood, Mattock, Reid, Thorne.
CARDIFF (4-4-2): Marshall; Quinn, Gerrard, Hudson, McNaughton (Kennedy 84); Burke, Scimeca (Wildig HT), Rae, Whittingham; Chopra, Etuhu (McCormack 59). Subs not used: Enkelman (gk), Matthews, Taiwo, Magennis.
GOALS: CARDIFF - Burke (18), Whittingham (85).
BOOKINGS: ALBION - Jara (handball 45+1), Olsson (foul 87). CARDIFF - Whittingham (handball 45+3), McNaughton (handball 63), Chopra (foul 90+1).
SENDING-OFF: ALBION - Carson (violent conduct 82).
REFEREE: P Taylor (Hertfordshire).
ALBION STARMAN: Graham Dorrans.
PIC: DISAPPOINTING NIGHT...Cox tussles with McNaughton