The Hammers defender headed a Mark Noble corner home to deny Leeds what would have been a vital three points in their quest to gatecrash the play-offs.
Collins’ leveller came just seven minutes after Luciano Becchio had put the home side ahead.
It capped a frantic finale after what until the final quarter had been a hard-fought encounter lacking in genuine goalscoring opportunities.
The best of those before Becchio’s strike came on 70 minutes when Paul Connolly brought a stunning save from Rob Green after meeting Ross McCormack’s corner with a deft header.
Five minutes later, West Ham also tested Andy Lonergan with a Gary O’Neil drive before the deadlock was finally broken seven minutes from time.
Becchio was the man in the right place at the right time to pounce after Connolly’s header had crashed against the crossbar and fire Leeds to a memorable victory.
The Hammers have the best away record in the Championship but they were largely held in check by their Yorkshire hosts.
Nicky Maynard missed the best chance of the first half on 23 minutes when, after being played through by Matt Taylor, the Hammers striker couldn’t beat Andy Lonergan.
The block drew deserved applause from the home fans, who earlier had looked on in horror as the United goalkeeper badly miscued a clearance and was fortunate to see the ball bounce off Maynard’s head to safety.
For Leeds, Robert Snodgrass went closest to breaking the deadlock with a curled free-kick that flew just inches past the post with Rob Green beaten.
Adam Clayton also shot just wide four minutes before the break after Abdoulaye Faye had failed to clear the danger before West Ham had an appeal for handball turned down, the fact Michael Brown suffered a bloody nose in the incident proving that the ball hit him in the face and not on the hand.
Warnock named an unchanged starting line-up as Leeds United prepared to welcome West Ham United to Elland Road.
It meant Danny Webber had to be content with a place on the bench along with Danny Pugh, Ramon Nunez, Zac Thompson and Mikael Forssell.
For the full report and reaction read Sports Monday, free inside your Yorkshire Post.