Caleb Folan's winner at Eastlands allowed Wigan to leapfrog Manchester City and leave them on the fringes of the Premiership drop zone.
Folan wheels away to celebrate a priceless goal
Folan took advantage of a static City defence to plant in an unmarked header.
Lee McCulloch earlier blasted over from eight yards and Wigan should have killed the game off by the interval.
City lacked a creative spark and a set piece provided their best chance, with Emmerson Boyce clearing Micah Richards' header off the line.
Mentally, City looked still on the beach in Dubai on their mid-winter break as Wigan completely bossed the first five minutes.
In fact, one of City's first touches of the ball denied Wigan a goal when Michael Ball bravely threw himself in front of Luis Antonio Valencia's powerful half-volley to block an almost certain goal.
Wigan should have taken the lead on 10 minutes when Folan outstripped Sylvain Distin and pulled the ball invitingly back across goal for McCulloch who contrived to blast over an open goal from eight yards.
It was 19 minutes before City shrugged off their lethargy and fashioned an attack, but even then Ball's threatening low cross was an easy gather for John Filan as Georgios Samaras and Bernardo Corradi sauntered into the box like a couple of Sunday churchgoers.
But their reaction was electric compared to that of City's defenders as Wigan took the lead on 19 minutes.
Folan heads home as City defenders stand and watch
The Sky Blue stargazers watched as the ball looped up as Emile Heskey and Richard Dunne challenged for Leighton Baines' free-kick and the unchallenged Folan took advantage to head past the static Nicky Weaver.
Wigan should have had a penalty when Valencia was caught by Ball's high challenge and although referee Howard Webb gave a free-kick inches outside, replays showed the foul was inside the box.
Joey Barton's corners were City's biggest threat, and Boyce came to Wigan's rescue when he cleared Richards' header off the line.
Strangely, the half-time whistle would have left Wigan boss Paul Jewell the more worried as his side had not killed the game off, while Stuart Pearce would know that City could not play as badly in the second half. Could they?
Pearce threw on new signing Emile Mpenza at half-time for the ineffective Samaras, and the Belgian would have got on the end of DaMarcus Beasley's teasing cross but for a crucial touch from Matt Jackson.
Wigan's enforced substitution saw McCulloch thrust up front to replace Heskey and it almost paid dividends as McCulloch fired in a snap-shot which drew a fine save from Weaver.
Barton tried to drive City on but after winning a tackle and taking a return pass from Corradi he scuffed a bobbling shot into Filan's hand and the Australian keeper then saved with his legs from Beasley.
Neither Filan nor Mpenza were prepared to pull out as a cross came in and it was the Wigan keeper who won out.
For all their increasing pressure City created few chances, with Wigan overcoming the disruption of the loss of Boyce to injury to provide an effective screen in front of Filan.
Man City boss Stuart Pearce:
"For the first 20 minutes we didn't compete and it was only a matter of time before they scored.
"Our biggest problem this season has been in front of goal, we haven't scored enough to be competitive.
"We have plenty of talent in the squad but Wigan proved you also need endeavour to win games."
Wigan manager Paul Jewell:
"We'll only know how important that is at the end of the season and there's a long way to go.
"It drags them into it and the more teams we can do that to, the better it is for us.
"The most pleasing thing was a clean sheet and three points against a team down there with us."
Man City: Weaver, Richards, Dunne, Distin, Ball (Sturridge 86), Trabelsi (Jihai 33), Barton, Ireland, Beasley, Samaras (Mpenza 46), Corradi.
Subs Not Used: Isaksson, Hamann.
Booked: Ball, Trabelsi, Dunne.
Wigan: Filan, Taylor, Jackson, Boyce (Unsworth 77), Baines, Valencia (Aghahowa 75), Landzaat, Skoko, McCulloch, Heskey (Kilbane 55), Folan.
Subs Not Used: Nash, Cotterill.
Booked: Taylor, Baines.
Goals: Folan 18.
Referee: H Webb (S Yorkshire).