A disappointing Chelsea held off a determined Wigan to grind out a win courtesy of Deco's 25-yard free-kick.
The midfielder scored after just three minutes when he found the top corner after Lee Cattermole had handled.
But Wigan hit back and Blues keeper Petr Cech had to pull off smart saves to keep out shots from Wilson Palacios and Amr Zaki.
Chelsea struggled for form but held on for a win as Cech again rescued them by keeping out a late Olivier Kapo strike.
The Blues had steamrollered Portsmouth 4-0 in their season-opener last week and Wigan seemed in danger of a similar fate after conceding an early lead.
Wigan keeper Mike Pollitt, who was a late promotion to the starting line-up following an injury to Chris Kirkland in the pre-match warm-up, may have been disappointed not to have kept Deco's effort out.
But Chelsea were uninspiring overall and the goal proved to be a rare moment of quality from the visitors.
In contrast, Wigan were galvanised by going behind and responded by taking the game to Chelsea.
Latics left winger Palacios gave Chelsea a taste of things to come when he wriggled his way past Jose Bosingwa and angled in a drive, which Cech blocked away.
Jason Koumas then showed his eye for a pass when he played Zaki through on goal but the Egyptian's well-struck shot was parried by Cech.
The loose ball just evaded the on-rushing Emile Heskey, who would have had the simple task of sidefooting in if Cech's save had rolled into his path.
Cech pushed Emmerson Boyce at a corner and escaped conceding a penalty and, although Ricardo Carvalho headed over at the other end, Chelsea struggled to match the tempo of the JJB Stadium side.
Wigan's quick passing and a clever Palacios backheel gave Zaki another sight of goal and Cech had to save well to keep out his shot.
The Latics' failed to carry their early enthusiasm into the second half as Chelsea nullified their threat..
606: DEBATEWigan grabbed a late equaliser to damage Chelsea's title push towards the end of last season but a goal proved elusive this time around.
The home side did manage to work an 88th-minute chance when Kapo unleashed a long-range strike, but Cech again saved his side by steering the ball wide.
Wigan boss Steve Bruce:
"The top teams only lose two or three games a season and we have missed an outstanding chance.
"Chelsea have had a bad day in my opinion, but one piece of brilliance by Deco has won it for them.
"Our keeper has hardly had a save to make. My players gave me everything they had apart from a goal."
Chelsea boss Luiz Felipe Scolari: "Deco is an intelligent boy. Why is he one of the best in the world? Because he is very clever. It was a very good goal.
"We didn't play well because we didn't pressure Wigan.
"This is my first test away from Stamford Bridge. What I expected I saw out on the field. In England you never say first versus last is easy."
Wigan: Pollitt, Melchiot (Camara 85), Boyce, Bramble, Figueroa, Valencia, Cattermole, Palacios (Kapo 80), Koumas (De Ridder 46), Heskey, Zaki.
Subs Not Used: Nash, Sibierski, Kilbane, Brown.
Booked: Cattermole.
Chelsea: Cech, Bosingwa, Carvalho, Terry, Ashley Cole (Bridge 83), Ballack, Essien, Lampard, Deco, Anelka (Malouda 89), Joe Cole (Kalou 58).
Subs Not Used: Hilario, Ivanovic, Alex, Belletti.
Booked: Terry, Carvalho.
Goals: Deco 4.
Att: 18,139
Ref: Alan Wiley (Staffordshire).
BBC Sport Player Rater man of the match: Titus Bramble on 6.93 (on 90 minutes).
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