Lee Bowyer struck his first goal for West Ham to rescue a point for the hosts and deny high-flying Wigan a third straight victory at Upton Park.
Zamora's progress is checked by Scharner at Upton Park
Despite a wealth of possession for the Hammers it was Wigan who created the clearer chances, Jason Koumas hitting a post and Julius Aghahowa going close.
Mark Noble's penalty appeal was turned down at the other end, before Paul Scharner volleyed a fine Wigan opener.
However, Bowyer secured a draw minutes later, clipping in from the angle.
It was no more than West Ham deserved from a topsy-turvy encounter, during which both sides' attacking frailties were exposed.
Wigan came into the match knowing anything other than a defeat would not only keep them in the upper reaches of the table, but also extend their best start to a Premier League season.
But it was the hosts that made nearly all the running in the first half.
With Kieron Dyer enjoying the freedom of Upton Park and Noble picking passes, the Hammers barely allowed Wigan a touch in the early stages.
And it was the latter that created the hosts' first chance of the afternoon when his clipped right-wing cross was glanced narrowly wide by Anton Ferdinand.
George McCartney also blazed over but clear-cut chances were at a premium, though Noble had strong appeals for a penalty turned down when he crumpled under the challenge of Andreas Granqvist two yards out on the half hour.
Replays suggested there was slight contact, but it would have been harsh on the Swedish defender.
There was less confusion about the officials' decision minutes later, though, when Craig Bellamy strode through to slot home only to be denied - correctly - by the linesman's flag.
Scharner's goal looked to have handed Wigan all three points
However, despite having to hang on for long periods in the half, it was Wigan that came closest to opening the scoring just before the break when Koumas cut in from the left and fired onto the post from 20 yards.
The goal would have been against the run of play, but the pattern continued after the break with West Ham dominating possession but Wigan creating the better chances.
Aghahowa, fairly anonymous in the first half, was the main aggressor for Wigan.
And he should have done better when he broke free of the defence only to take a poor touch and allow Robert Green to smother his shot.
The Nigerian was again denied by Green on the hour when the keeper blocked his snap shot from six yards, with Mario Melchiot heading the follow-up wide of the target with the goal gaping.
Still West Ham huffed and puffed but, with Granqvist and Titus Bramble looking increasingly comfortable, it appeared the hosts' hopes of rewarding their superiour possession with a goal were fading.
And their worst fears looked to have been realised 12 minutes from time when Scharner broke the deadlock with a wonderful finish, firing an overhead kick into the corner from Emile Heskey's knockdown to hand Wigan the lead.
It looked like West Ham's toothless attack would once again cost them the points, but Bowyer had other ideas and, having gone close from a Boa Morte pull-back minutes earlier, grabbed the leveller with a clipped shot into the corner from the Portuguese winger's fine pass on 81 minutes.
An expected home rally ensued as West Ham pressed for a winner but, other than a muted appeal for a penalty when Dyer fell under Bramble's tackle, they could not trouble the Wigan goal and it finished all square.
West Ham boss Alan Curbishley:
"We're a little frustrated by a draw but I guess I have to be delighted we've got something from the game after falling behind so late.
"In the first half they put lots of men behind the ball and we struggled to break them down, whereas in the second it changed and they began to get a few chances on the break.
"A point was probably a fair result and I'm delighted that Lee's got a goal - it's all that's been missing from his play for me."
Wigan manager Chris Hutchings:
"We cancelled eachother out to a certain extent, but this is a tough place to come and I think we deserved a draw because of the chances we created.
"We came under a lot of pressure at times but we held out and restricted them to half chances.
"That's our first away point of the season and that's important. We're on the right road."
West Ham: Green, Neill, Ferdinand, Upson, McCartney, Dyer,
Noble, Mullins (Bowyer 65), Etherington, Zamora (Ashton 61),
Bellamy (Boa Morte 75).
Subs Not Used: Walker, Spector.
Goals: Bowyer 81.
Wigan: Kirkland, Melchiot, Bramble, Granqvist, Kilbane,
Valencia (Brown 77), Scharner, Landzaat, Koumas,
Sibierski (Aghahowa 38), Heskey.
Subs Not Used: Pollitt, Hall, Folan.
Booked: Landzaat, Brown.
Goals: Scharner 78.
Ref: Andre Marriner (W Midlands).