Match ends, Leicester City 1, West Ham United 1.
Wilfred Ndidi scored a 89th-minute equaliser to break West Ham's resolve after they looked set to take all three points despite Mark Noble's first-half sending-off.
Centre-back Fabian Balbuena had put the visitors in the lead, reacting first to the rebound from his own header, to prod home after 30 minutes.
Just eight minutes later Noble was shown a straight red card for a high, lunging tackle on Wilfred Ndidi.
West Ham frustrated Leicester, while Lukasz Fabianski made some crucial second-half saves.
Jamie Vardy had dominated the pre-match discussion, with reports the former England striker was angry at being dropped for the game.
The 31-year-old, who was forced off against Arsenal on Monday with a stomach bug, started the game on the bench and Leicester manager Claude Puel said the player was not "100% fit", despite Vardy declaring himself so via Instagram on Friday.
As it was, Vardy came on at half-time and offered more of an attacking threat. He went close with a header and late in the game had a fierce strike saved by Fabianski.
With the Hammers poised to take all three points, Ndidi's long-range shot took a wicked deflection off Balbuena to beat Fabianski.
There was concern at the end of the game, as Leicester right-back Daniel Amartey left the pitch on a stretcher in injury-time in some pain with an injury to his ankle.
Puel addressed the Vardy rumours at the end of the game, he said: " I don't know why it is a problem.
"I wanted him to come on in the second half to win the game. I have to manage his physical being. It is difficult to play him when he isn't 100%."
Tough times for Puel
Puel celebrated a year in charge at the King Power this week, but left the pitch on Saturday to boos.
The Frenchman had gone into the game on the back of four defeats in his last six league games and his team sheet raised eyebrows before kick-off, making four changes from the team that at lost 3-1 at Arsenal on Monday.
Selecting Kelechi Iheanacho, instead of Vardy, was the most eye-catching choice and the Nigerian barely threatened in the game, apart from when he was flagged for offside in the second minute, having swept the ball into the back of the net.
Vicente Iborra had the Foxes best chance in the first half after Noble's red, but his header was straight at Fabianski.
Vardy's second-half introduction gave his side more control, sharpness and pace in attack, but still Leicester toiled.
They had a flurry of chances, 21 shots in total, with 15 coming in the second half, but many were either from long range or offside - they were flagged seven times in the match.
Harry Maguire hit the crossbar with a header on 67 minutes and Fabianski kept out Marc Albrighton twice.
Puel introduced Shinji Okazaki for Turkish centre-back Caglar Soyuncu with 10 minutes remaining and finally got the breakthrough via Ndidi.
After getting back into the game, Leicester almost threw it away minutes later as Angelo Ogbonna shot over from a few yards out.
"I was happy with the second half because it was a good mentality and there was quality on the pitch," said Puel. "We showed two faces in our game and of course, we need to resolve this."
Depleted Hammers impress
The news this week that Ukrainian winger Andriy Yarmolenko would be out for six months with an Achilles injury, was the latest blow to the club already struggling with a long injury list.
They were dealt a further blow by the news Marko Arnautovic would miss the game through sicknesses.
After withstanding Leicester's early attacks they grew into the game and after Balbuena's opener, defended magnificently.
This was a match built on their defence, with Javier Hernandez cutting a frustrated figure up top, as he became increasingly isolated.
Declan Rice epitomised their efforts, excelling in the holding midfield role and protecting the back four.
The faces on the players after Ndidi's goal told the story, as they saw the result as three points lost.
"It was gutting to concede so late," said Rice. "If we would have come away with three points we would have been delighted but we can build up on this."
Manager Manuel Pellegrini said his side were "unlucky" with the goal, adding: "I am happy with the performance and the way the team played but not with the result.
"We drew against Leicester away with one player less which can be seen as a good result but the mentality of the players want more."
Man of the match - Declan Rice
Leicester are in Carabao Cup action on Tuesday night, as they host Southampton, before returning to league action against Cardiff on Saturday.
West Ham face Tottenham in the EFL Cup on Wednesday followed by the visit of Burnley in the league on Saturday.
Hammers can't hold on to lead - stats
- West Ham have picked up just eight points from their opening 10 league games this season; only twice before in the Premier League have they had fewer at this stage (seven in 2009-10, six in 2010-11)
- West Ham have now lost eight points from leading positions in this season's Premier League, more than any other side
- West Ham's Fabian Balbuena is the fifth different Paraguayan player to score in the Premier League (excluding own goals), and the first since Antolin Alcaraz for Wigan against Blackburn in May 2012
- Wilfried Ndidi's goal for Leicester was his first in the Premier League since May 2017 against Watford, 539 days ago. All three of his goals in the competition have come at the King Power Stadium
- 18AmarteySubstituted forat 90+4'minutes
- 4SöyüncüBooked at 47minsSubstituted forOkazakiat 80'minutes
- 31GhezzalSubstituted forVardyat 45'minutes
- 8IheanachoSubstituted forGrayat 61'minutes
- 14Ricardo Pereira
- 5ZabaletaBooked at 85mins
- 45DianganaSubstituted forCresswellat 75'minutes
- 16NobleBooked at 38mins
- 8Felipe AndersonSubstituted forOgbonnaat 81'minutes
- 17HernándezSubstituted forAntonioat 61'minutes
- Michael Oliver
- Shots on Target
Second Half ends, Leicester City 1, West Ham United 1.
Attempt blocked. Marc Albrighton (Leicester City) left footed shot from the centre of the box is blocked.
Attempt saved. Shinji Okazaki (Leicester City) header from the centre of the box is saved in the centre of the goal. Assisted by Ben Chilwell.
Daniel Amartey went off injured after Leicester City had used all subs.
Delay over. They are ready to continue.
Delay in match Daniel Amartey (Leicester City) because of an injury.
Attempt missed. Angelo Ogbonna (West Ham United) left footed shot from the centre of the box is high and wide to the left. Assisted by Robert Snodgrass.
Goal! Leicester City 1, West Ham United 1. Wilfred Ndidi (Leicester City) right footed shot from outside the box to the top left corner. Assisted by Demarai Gray.
Attempt saved. Jamie Vardy (Leicester City) right footed shot from the centre of the box is saved in the centre of the goal.
Offside, Leicester City. Ben Chilwell tries a through ball, but Shinji Okazaki is caught offside.
Attempt saved. Michail Antonio (West Ham United) right footed shot from the centre of the box is saved in the bottom right corner.
Pablo Zabaleta (West Ham United) is shown the yellow card for a bad foul.
Offside, Leicester City. Marc Albrighton tries a through ball, but Jamie Vardy is caught offside.
Corner, Leicester City. Conceded by Aaron Cresswell.
Offside, Leicester City. Demarai Gray tries a through ball, but Shinji Okazaki is caught offside.
Attempt missed. Angelo Ogbonna (West Ham United) header from the centre of the box misses to the right. Assisted by Robert Snodgrass with a cross following a set piece situation.
Substitution, West Ham United. Angelo Ogbonna replaces Felipe Anderson.
Substitution, Leicester City. Shinji Okazaki replaces Caglar Söyüncü.
Foul by Caglar Söyüncü (Leicester City).