A David Cotterill strike and a Jonathan Spector own goal fired Wigan to victory in a lively encounter at West Ham.
Cotterill celebrates his goal at Upton Park
Cotterill opened the scoring with a fine turn and shot into the top corner after Wigan counter-attacked following a Carlos Tevez shot which hit the post.
Leighton Baines' 30-yard half-volley flew in off Jonathan Spector to put Wigan two up.
Marlon Harewood saw a good shot saved by Chris Kirkland early on and Tevez spurned several chances for West Ham.
The game was barely a minute old when West Ham goalkeeper Robert Green was forced to make a save, pushing the ball on to the post from a Paul Scharner flick-on.
Green was in the thick of it again shortly afterwards when he hit Hayden Mullins' under-hit back pass against Wigan's Lee McCulloch, but the ball flew wide.
Hammers striker Harewood drew a save from Chris Kirkland at the other end after Nigel Reo-Coker set up his colleague with a pass threaded through Wigan's defence.
The home crowd came to life when Tevez, still seeking his first West Ham goal, was just unable to reach a Paul Konchesky cross from the left.
Chances then came in quick succession at both ends as David Cotterill of Wigan and Harewood both flashed shots across the face of goal.
West Ham had the better of the remainder of the first half, with Tevez again unable to get a good connection when Yossi Benayoun swung a corner towards him at the far post.
The unlucky Tevez had the first chance of the second half as his deflected shot from the edge of the area came back off the inside of the post.
The pain was compounded for West Ham as Wigan immediately burst up the pitch and, collecting Kevin Kilbane's clever pass across the box, Cotterill turned his marker and fired into the top corner to put Wigan ahead.
It got worse for West Ham when a cleared corner fell to Baines, who hit a 30-yard half-volley which was perhaps going wide, but hit Spector and flew past Green.
Hammers manager Alan Pardew responded immediately by replacing Benayoun with Teddy Sheringham, who had his first chance five minutes later but lashed a free-kick over the bar.
Scharner thought he had put Wigan three up when he headed home from close range but his effort was ruled - perhaps incorrectly - offside.
West Ham struggled to make chances from there on in, Harewood's failure to put Tevez through summing up their frustrating evening.
The hard-working Tevez also saw his late free-kick deflected off the wall as Wigan held firm for victory.
West Ham boss Alan Pardew:
"We did not give a display worthy of ourselves. On behalf of the players I apologise to the fans, who have paid good money tonight.
"Their status as Premier League players is under threat and we have to stand up and be counted.
"They had better realise it. When they get home tonight and see the league table it will soon sink in."
Wigan boss Paul Jewell:
"It was a big show of character from our lads.
"We were embarrassed at the weekend and I asked them to show their character tonight. We controlled the game from start to finish.
"It was a very good away performance. When you come to a place like West Ham, with a hostile crowd, you have got to silence them and we did that."
West Ham: Green, Spector, Ferdinand (McCartney 68), Collins, Konchesky, Benayoun (Sheringham 58), Mullins, Reo-Coker, Etherington (Bowyer 82), Harewood, Tevez.
Subs Not Used: Carroll, Zamora.
Wigan: Kirkland, Wright, Boyce, Hall, Baines, Cotterill (Camara 80), Scharner, Skoko (Landzaat 75), Kilbane, Heskey, McCulloch.
Subs Not Used: Pollitt, Johansson, Webster.
Booked: Skoko, Cotterill, Scharner.
Goals: Cotterill 51, Spector 58 og.
Ref: A Wiley (Staffordshire).