West Ham captain Nigel Reo-Coker put an exclamation point on a week to remember for boss Alan Pardew's side by grabbing an injury-time winner in their 2-1 success at Wigan.
It is now five defeats and a draw for Wigan in their last six games at the JJB Stadium since an enthralling 4-3 victory over Manchester City on Boxing Day.
Wigan had taken the lead at the end of the first half to a bullet of a strike from Lee McCulloch, and looked set to end their barren home run.
But it was a come-from-behind performance from the Hammers as they hit back after the break with goals from Marlon Harewood and Reo-Coker's last-gasp strike.
Wigan manager Paul Jewell had spoken ahead of the game of West Ham's desire to finish above the Latics this season with safety secured, and there is every chance of that now.
Certainly this season has been one that has exceeded expectations for both clubs following promotion from the Coca-Cola Championship last May.
Despite a trouncing in the Carling Cup final to Manchester United, Wigan's achievement in reaching the showpiece occasion cannot be underestimated.
Now the Hammers are poised to follow suit in the FA Cup final, with Pardew's side facing a semi-final showdown with either Charlton or Middlesbrough.
With such a prestigious occasion looming for United in three weeks, there could be no excuses from Pardew in terms of his line-up.
Showing just one change from the team that beat Manchester City in a quarter-final tie on Monday - Lionel Scaloni in for Christian Dailly due to a hamstring injury - it was a West Ham side whose confidence should have been soaring.
But Wigan have shown scant regard for reputations over the course of what has been an astonishing season, and although the first half was a tepid affair, they had their noses in front by the end of it.
Shaka Hislop had been tested on three occasions as Wigan carved out the best of the few opportunities that arose before being caught by a searing strike from McCulloch.
The Trinidad and Tobago international had earlier showed exceptional handling in holding onto crisp strikes from Gary Teale in the third minute and then former Hammer Jimmy Bullard, who had curled in a low free-kick from 25 yards.
McCulloch served notice of his intent by forcing Hislop into another smart save on the stroke of half-time as the Scot had let fly with a first-time shot from 20 yards.
But there was nothing the Hammers goalkeeper could do about the shot that followed in the first minute of the two played for injury time.
Teed up by a searching run and pass from Bullard, McCulloch then took one touch before powering a drive past Hislop that had such power the goalkeeper never moved as it flew past him.It was just about deserved as West Ham's chances had been restricted to two, with the first in the ninth minute when Paul Konchesky's raking 30-yard left-foot drive shaved the post.
• 'A fantastic week'
The second was fortuitous as goalkeeper John Filan and Pascal Chimbonda collided on the edge of the area in chasing a loose ball, thanks in part to Harewood's shove on the Latics right-back.
With Filan stranded, the ball ran to Matthew Etherington wide on the left, but his attempted chip from 30 yards was wide.
Such good fortune, though, continued after the break with West Ham equalising seven minutes after the interval.
They should have been 2-0 down seconds before Harewood struck as Henri Camara was presented with a clear sight of goal after using his pace to burst into the area.
But with only the goalkeeper to beat, the Senegal striker drove his shot into the arms of Hislop, who immediately launched a counter with a long punt upfield.Following a flick-on by one-time Wigan target Dean Ashton, covering defender Paul Scharner's diving header on the edge of the area back to Mike Pollitt was weak.
Pollitt, in his first game back since sustaining a hamstring strain in the Carling Cup final, had replaced Filan at the interval due to an eye injury.
But in attempting to cover for Scharner's error, Harewood nipped in to flick the ball virtually out of Pollitt's hands before tapping home his 15th goal of the season into an empty net.
Scharner, McCulloch, Camara and substitute David Thompson had the chances that followed to have edged Wigan back in front.
But with virtually the last kick of the game, Reo-Coker turned home a low cross from sub Teddy Sheringham for his third of the season to nick it at the death.
• Pardew happy after 'fantastic week'
West Ham snatched a last-gasp victory at Wigan to keep their Barclays Premiership season burning bright - but FA Cup glory is all that matters for manager Alan Pardew.
'The win on Monday and the draw, followed by this result, it has been a fantastic week for West Ham,' said Pardew.
'Although after the first half I wasn't feeling quite as punchy as I am now because I was very disappointed.
'That was reflected in the dressing room, not just by myself but by some of the players. It wasn't good enough for us.
'You could see the hangover in the first half, but in the second we were more like ourselves, and this was a great win for us.
'But at the moment we have achieved nothing other than showing fantastic potential.
'We have hit one major goal in staying in the Premiership, and now there's a chance of glory and as a team we have to grasp that opportunity that is right in front of us.
'The FA Cup is a chance to win a trophy. Sixth or seventh place in the Premiership doesn't really enthral me as much as winning a piece of silverware for this great club.
'But we know the bread and butter of what we are all about is in the league.
'Our supporters made that very clear last week after the defeat at home to Portsmouth, that they won't accept any performance below the level, and rightly so.'
Wigan came into the game on the back of successive 1-0 away wins at Sunderland and Manchester City, but it is their home form that is now becoming a major concern for manager Paul Jewell.
The Latics have lost five and drawn one of their last six league games in front of their own fans since the 4-3 win at home to Manchester City - and that was on Boxing Day.
Recognising that, Jewell said: 'We've not been great at home since the turn of the year.
'It's something that needs to be addressed for next season because it's going to be a lot tougher than this one - if that's possible.
'We are eighth in the table and we have done brilliantly, but our goal difference this season is minus two.
'That means we are either conceding too many goals, or not scoring enough, or maybe a bit of both.
'Other than the four we scored against Manchester City and the three against Charlton Athletic, we have found it a struggle to score goals at home but we knew it would be difficult coming into this league because the hardest thing in football is putting the ball in the back of the net.
'But we are actively trying to improve the squad for next season, although I will only bring players in that will improve the squad. I don't want to play the numbers game.'
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