The Warriors looked weak in defence and clueless in attack as they crashed to their fourth successive defeat.
Huddersfield, who opted to bring back Lee Gaskell, Joe Wardle and Akuila Uate, started the strongest and had the Warriors on the ropes for the opening 10 minutes as they forced three dropouts to camp out in Wigan’s half.
The visitors deservedly went ahead after 12 minutes when Kruise Leeming finished off a fine move involving Aaron Murphy, Matt Frawley and Ukuma Ta’ai. Gaskell added the extras as the visitors led 6-0.
The Giants should have extended their lead before the break as Jermaine McGillvary headed for the line only to be brought down by a great double cover tackle from Zak Hardaker and Oliver Gildart, while video referee James Child judged that Suaia Matagi had lost control of the ball as he attempted to score.
Wigan were level after 53 minutes when Morgan Escare raced ahead to collect a Thomas Leuluai kick to go under the posts, with Hardaker converting to make it 6-6.
Wigan had to spend 10 minutes a man down after Taulima Tautai was sinbinned for kicking out. Gaskell slotted over the penalty to make it 8-6.
Uate went close to increasing the Giants’ lead before they finally got the second try their performance deserved as Joe Wardle went over from close range. Gaskell’s conversion put them eight points ahead with 15 minutes to go and sealed a famous win.
Wigan Warriors: Hardaker, Manfredi, Hankinson, Gildart, Marshall, Williams, Leuluai, Clubb, Powell, Flower, Isa, Paisley, O’Loughlin. Substitutes: Bullock, Tautai, Hamlin, Escare.
Huddersfield Giants: McIntosh, McGillvary, Turner, J. Wardle, Uate, Gaskell, Frawley, Ikahihifo, Leeming, Ta’ai, J. Wardle, Mellor, Murphy. Substitutes: O’Brien, Roberts, Matagi, Lawrence.
Referee: Robert Hicks (RFL).