MARC-Antoine Fortune leapt off the bench to earn Albion what could prove a vital point with a 79th-minute leveller.
The Baggies got off to a dream start when Peter Odemwingie poked them ahead with his ninth of the season in the fifth minute.
But Wigan went into the break ahead courtesy of two free-kicks. Charles N'Zogbia levelled with a deflected effort on 20 before former Baggies loanee Ben Watson made it 2-1 two minutes before half-time.
It was end-to-end stuff after the break but Albion gradually got on top and put the Wigan goal under concerted pressure.
Roberto Di Matteo's men, who recorded a whopping 17 efforts at goal, deservedly levelled when Fortune, who along with Chris Brunt had earlier hit the woodwork, headed home man-of-the-match Jerome Thomas' centre.
There was to be more penalty agony for the Baggies in stoppage time when they had two strong appeals turned away - but the Latics somehow held on.
Carlos Vela was given a rapturous pre-match welcome as he made an immediate debut in one of two changes from the Blackburn defeat nine days ago.
Simon Cox also made his first Barclays Premier League start in almost three months, with James Morrison and Gabriel Tamas making way.
Steven Reid returned to the bench after a month-long knee injury lay-off.
Roberto Martinez made three changes from their last league game as Gary Caldwell, Watson and Mohamed Diame came in for Hendry Thomas, Steven Caldwell and James McArthur.
The stakes were high on a cold Black Country night as 16th entertained 18th - separated by only three points.
But Albion were boosted by a sell-out home crowd after the club's reduced ticket prices proved a big hit.
And they were soon on their feet as Odemwingie broke the deadlock inside five minutes.
Thomas spearheaded a Baggies break before slotting the striker in behind Steve Gohouri and the Nigeria international coolly prodded the ball first time past the helpless Ali Al Habsi.
It was the first time Albion have scored the first goal in nine games.
N'Zogbia tried to restore parity three minutes later but failed to trouble Boaz Myhill's goal with an ambitious 35-yard free-kick.
But Albion had started with a real purpose and Caldwell had to produce a vital near-post clearance after terrific link-up play between Odemwingie, Vela and Gonzalo Jara down the right.
The Baggies threatened again on 17 when Jonas Olsson headed just wide from skipper Chris Brunt's free-kick.
But the visitors were level three minutes later.
After Youssouf Mulumbu had fouled N'Zogbia on the edge of the Baggies box, the winger dusted himself down and saw his left-footed free-kick clip Mulumbu on the edge of the wall and fly into the far bottom corner, giving Myhill no chance.
It was Wigan's turn to enjoy a spell in their opponents' half but Albion defended resolutely and it was the hosts who threatened next on 29.
Thomas was again the architect as he threaded in Vela down the right, but the Mexican international decided to shoot first time and fired weakly at Al Habsi from 18 yards.
Wigan stormed straight upfield and Myhill had to be on his toes to beat away danger-man N'Zogbia's stinging near-post drive after he had shrugged off three Albion challenges.
Back came the Baggies and Brunt dragged his shot just wide of the near post from 25 yards.
But Albion were behind on 43 - from another free-kick.
Watson swung a terrific ball from the left-flank into the Baggies box which evaded everyone before nestling inside the far bottom corner.
Albion almost equalised in the third minute of stoppage time when Odemwingie ghosted onto Brunt's deep centre and saw his six-yard volley blocked at point-blank range by Maynor Figueroa.
In the ensuing melee, Mulumbu had a 15-yard effort deflected wide.
The Baggies attacked from the re-start and went close inside 27 seconds when Marek Cech smashed Vela's lay-off just over from 20 yards.
But Wigan soon threatened themselves and Myhill had to pull off a smart save to deny Franco Di Santo, who had outmuscled ex-Wigan ace Paul Scharner as they chased a high ball. The rebound fell to Hugo Rodallega who blazed well over from 15 yards.
The action soon swung to the other end and Al Habsi could only watch as Thomas charged into the box and curled just over from 15 yards after collecting Brunt's clever lay-off.
Mulumbu was the next to try his luck but he too was off target, this time from 25 yards.
Thomas was proving Albion's best outlet and he jinked inside Emmerson Boyce before shooting tamely at Al Habsi, who gathered at the second attempt before Odemwingie could pounce.
But chances were coming at the other end too and Myhill did well to deny N'Zogbia with his feet after the ex-Newcastle winger had charged across the box.
Albion had another let off moments later when Rodallega exchanged a great one-two with Mohamed Diame before blasting just over from 15 yards.
Back came the Baggies but Scharner saw an ambitious overhead free-kick from Cox's corner loop harmlessly wide.
Albion began to lose their way but sub Fortune gave them renewed hope when he turned sharply and smashed the base of the near post from 20 yards on 73.
Incredibly, just two minutes later, Brunt hit the same post from 25 yards after a terrific run by Odemwingie.
But their luck finally changed 11 minutes from time when they levelled after Wigan failed to properly clear a Baggies corner.
Mulumbu worked the ball wide to Thomas and his cross was expertly headed home by Fortune from eight yards.
Albion pummelled Wigan during the final minutes.
Thomas' shot was deflected just wide by Boyce before Al Habsi pulled off the save of the game to keep out Olsson's header from Brunt's corner.
Wigan did threaten on 85 when the unfortunate Fortune deflected Rodallega's cross to N'Zogbia - but the winger blazed over from 15 yards.
Albion thought they should have had a penalty when Caldwell inadvertently sliced a clearance onto his own arm and they had more appeals turned away when Gohouri appeared to foul sub Reid.
Mulumbu saw an effort brilliantly kept out at the near post by Al Habsi - but Wigan held on.
ALBION (4-1-2-2-1): Myhill; Jara (Reid 77), Scharner, Olsson, Cech; Mulumbu; Brunt, Cox (Fortune 65); Vela (Tchoyi 58), J Thomas; Odemwingie. Subs not used: Carson (gk), Morrison, Shorey, Ibanez.
WIGAN (4-3-3): Al Habsi; Gohouri, G Caldwell, Boyce, Figueroa (S Caldwell 71); Diame, Watson, McCarthy (H Thomas 62); Rodallega, Di Santo (Moses 76), N'Zogbia. Subs not used: Pollitt (gk), Gomez, McArthur, Stam.
GOALS: ALBION - Odemwingie (5), Fortune (79). WIGAN - N'Zogbia (20), Watson (43).
BOOKINGS: ALBION - Odemwingie (foul 37), Jara (foul 43), Mulumbu (unsporting behaviour 85), Brunt (foul 90+3). WIGAN - Watson (foul 16), H Thomas (foul 65), Rodallega (kicking ball away 83), Gohouri (time wasting 90+2).
REFEREE: P Dowd (Staffordshire).
ALBION STARMAN: Jerome Thomas.
PIC: BRIGHT START...Cox and goalscorer Odemwingie celebrate Albion's early opener