Third-placed Chelsea appeared to be coasting to a victory which would have seen them move to within four points of leaders Manchester City after Daniel Sturridge's 59th-minute strike put them 1-0 up at the DW Stadium.
But with just two minutes of normal time remaining, Cech made a dreadful hash as he stooped to gather Hugo Rodallega's low cross and Spanish midfielder Jordi Gomez was on hand to jab home the equaliser.
It was a bitterly disappointing outcome for Chelsea, who had beaten leaders City last week and who looked to be heading for a fourth consecutive league victory after Sturridge's goal.
"It's a disappointing result," Chelsea manager Andre Villas-Boas said. "Just a few minutes from the end we conceded a goal.
"In the last moments if we'd kept the ball a bit better we could have taken the three points, but Wigan pushed hard and they got the goal they deserved. It was a fair result.
"I think it's always a battle in the Premiership. We didn't get the three points we thought we could get."
Wigan boss Roberto Martinez meanwhile praised his struggling side's team spirit.
"Today the performance was perfect. This was a real reward for all the hard times over the last few months," Martinez said.
In earlier games Saturday, Bolton's grim slide continued as Owen Coyle's team crashed to a fifth consecutive loss with a 2-0 defeat at Fulham.
Bolton's hopes of bagging a crucial three points were effectively ended midway through the first half at Craven Cottage as Fulham went 2-0 up courtesy of goals from Clint Dempsey and Bryan Ruiz.
Dempsey fired Fulham ahead on 32 minutes, the American international heading home after a fine run and cross from Ruiz.
Moments later Ruiz made it 2-0 after latching on to Dempsey's pass before chipping over Jussi Jaaskelainen.
Coyle later bemoaned his team's failure to make the most of a bright start.
"We have let the opportunity pass us by and it's getting repetitive saying the same things," Coyle said.
"It's not like we are five or six games into the season. We've made some mistakes and we are in real dogfight now. Players must show passion and be ready to give better performances."
Bolton's Lancashire rivals Blackburn also remain anchored in the relegation mire after crashing to a 2-1 defeat at home to West Bromwich Albion, their sixth loss from eight home games this term.
West Brom's James Morrison fired the visitors ahead on 52 minutes, lashing in a volley from the edge of the area after Steven N'Zonzi failed to clear.
Morrison's strike was the cue for a chorus of boos as Rovers miserable season continued before defender Scott Dann bundled in an equaliser on 72 minutes to get Blackburn back on level terms.
Yet just as it looked as if Rovers had salvaged a point, Peter Odemwingie curled in a long-range winner on 89 minutes to make it 2-1.
The defeat was met with angry boos from Rovers fans, who have been demanding the dismissal of embattled manager Steve Kean.
Kean however insisted he would not bow to the pressure as his team prepare for a six-pointer against Bolton in midweek.
"The owners are fully behind me but I am sure they like the players, the staff and fans are disappointed," he said.
"We want to be winning games especially at home and it makes Tuesday's game (at home to Bolton) massive if it wasn't massive already."
Elsewhere Stoke fought back from 1-0 down to snatch a 2-1 victory over Wolves at Molineux.
Stephen Hunt fired Wolves ahead with a penalty on 16 minutes but Stoke hit back with a Kevin Doyle own goal before Peter Crouch scrambled in the winner on 70 minutes.
Promoted Norwich meanwhile continued their impressive run of form with a 1-1 draw at Goodison Park against Everton.
Grant Holt put the Canaries ahead on 28 minutes before a second half onslaught from the Toffees culminated with Leon Osman equalising for Everton on 81 minutes.
In the other early game, Newcastle were held to a 0-0 draw at home to Swansea.