Two-goal Darren Wrack pulled off a shock win for Walsall as Wigan's long unbeaten run came to an end at Bescot.
Wrack's second-half brace sentenced Wigan to their first defeat since the opening day of the season - ending an unbeaten sequence of 16 games.
After seeing his side secure a third successive home win, Walsall manager Colin Lee said: "I thought that some of our play in the second-half was outstanding.
"We want to make Bescot a hard place to come. We don't want people thinking they will get an easy game here and now we want to build on this good run of home form." Disappointed Wigan boss Paul Jewell said: "It was a disappointing way for our winning run to come to an end. We looked jaded and did not take advantage of the chances that we created.
"I am now looking for us to bounce back but I have still got to be pleased with the position we are in at this stage of the season." Wigan threatened to take a stranglehold on the match in the opening stages but found Walsall a tough nut to crack.
Geoff Horsfield was frustrated twice by some last-ditch defending in the opening ten minutes while his strike partner Nathan Ellington blazed wide from close range.
Having weathered the early storm, Walsall managed to work their way into the game and Simon Osborn was inches away from giving them the lead when his 13th minute drive flew inches wide.
But it was Wigan who looked by far the most potent side going forward and Walsall were indebted to goalkeeper James Walker for keeping them on level terms when he produced a stunning 38th minute save.
Walker dived low to his right to spectacularly push away a fierce shot from the dangerous Horsfield.
When Lee McCulloch headed narrowly wide 90 second into the second half, it seemed only a matter of time before Wigan broke the deadlock.
But their failure to make their chances pay was to cost them dearly after 50 minutes.
Wrack surged through the Wigan midfield and exchanged passes with skipper Paul Merson before continuing into the penalty area where he calmly lifted the ball over advancing goalkeeper John Filan.
It was a setback that Wigan never recovered from and Wrack sealed Walsall's success in the 66th minute - this time poking the ball home after a right-wing cross from Chris Baird.