Leeds had romped to a convincing 4-1 lead at the break courtesy of woeful defending and Harry Kewell's brilliance.
The winger orchestrated an opener for Nick Barmby that was soon levelled by Paolo Di Canio, but Kewell then grabbed two and Viduka an opportunist fourth to pile the pressure on already troubled Glenn Roeder.
However, The Irons showed their mettle in the second half and Di Canio won and converted a penalty before Trevor Sinclair got the crowd believing that a draw could be earned with a third from a corner.
West Ham were given a torrid time in the first half - with Leeds quickly asserting themselves and highlighting The Irons` deficiencies in defence.
The opener was swift with a long punt from Paul Robinson allowed to bounce and Kewell did well to turn the ball into Barmby's path and he gleefully headed home.
Wet Ham did get back in to the game, with Di Canio benefiting from a poor parry from Robinson, who saw a Michael Carrick shot late, to slot into the empty net.
But Leeds were not to be denied and Kewell went from architect to scorer when he was left unmarked at the near post to head home from a corner.
Kewell then grabbed his second and his side's third when a half cleared ball fell kindly and he volleyed home with aplomb - despite using his right foot.
If the first three goals had highlighted the problems that are sending jitters through the Upton Park faithful, the fourth showed that confidence is virtually absent.
Christian Dailly played a woeful pass back to David James, that the keeper did well to even reach.
However Viduka had been quick to react and his persistence paid off with a kind interception as James slid in - allowing the Australian to slot home gleefully into the untended goal.
But whatever Roeder said at half time certainly rallied the troops, and the foolish West Ham fans that left at half time must be rueing their rash decision.
Di Canio had already had a close penalty call thrown out when he lured Gary Kelly into a rash challenge in the area to give himself the chance to score his second from the spot.
Suddenly they had the momentum and West Ham put themselves back in with a chance when Sinclair lost his marker from a corner to superbly head home at the near post.
But try as they might The Hammers failed to grab the leveller, and Terry Venables will be delighted that his side could weather the storm and cling onto three crucial away points.
Although the defeat will pile pressure on Roeder, nobody will doubt the manager's ability to raise his players' game at half time.
It was just a shame for The Irons' fans that he could not do it before the opening 45 minutes cost them the game.
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West Ham v Leeds
