James Maddison scored after just eight minutes, and while Youri Tielemans would see a penalty saved, Harvey Barnes doubled the advantage as Leicester secured a sixth clean sheet in their last eight Premier League matches.
From City's 3-0 Carabao Cup success over Newport County, Brendan Rodgers made seven changes to his side, with Wout Faes, Luke Thomas, Boubakary Soumaré and Barnes the men to remain. The Foxes again wore poppy-adorned shirts, in support of the Royal British Legion, following the sounding of The Last Post upon a minute's silence before kick-off.
City, wearing their third kit, carved out the first opportunity of the match in the capital. Academy graduate Kiernan Dewsbury-Hall worked the ball well down the left and his cut-back found the feet of captain Tielemans, who set himself before drilling low at Łukasz Fabiański.
Within minutes, Leicester were in front, with Dewsbury-Hall again at the centre of it. Soumaré played a one-two with Maddison and released Barnes, who found Dewsbury-Hall, and while Patson Daka couldn't connect fully with his cross, the No.10 – confirmed in England's FIFA World Cup squad on Thursday – slammed in at the far post for his seventh Premier League strike of 2022/23.
Hammers captain Declan Rice was wayward with a long-range effort on 19 minutes as West Ham tried to respond to City's opener. From a similar distance, Daniel Amartey had a drive tipped over by Fabiański, who thwarted the Ghana international after a good run through midfield.
Leicester were forced into an early change after Maddison took a knock midway through the first period. Dennis Praet was the man to replace the No.10, who was unable to continue.
A superb sliding challenge from Amartey prevented Saïd Benrahma from getting an initial shot on goal, however the ball fell kindly for the Algeria winger, whose follow-up was saved by Danny Ward before the Wales 'keeper collected. The City No.1 was there again on the half-hour mark, gathering a delivery from Lucas Paquetá, who later blasted over from inside the box.
Paquetá was there again three minutes later, nodding Aaron Cresswell's cross wide of Ward's left-hand post, while Thomas got in the way of Jarrod Bowen's left-footed curler to send the ball behind. Soumaré eventually cleared his lines after a short corner-kick found its way into the area.
David Moyes' side thought they had got themselves on level terms with 10 minutes of the first half to play, however after Bowen had set up Tomáš Souček to fire home, the offside flag went up against the former just as the ball hit the back of the net. Ward was required to claw Paquetá's looping header away from the top corner not long after.
City then launched an immediate counter-attack. Zambia striker Daka led the charge, but his run was halted by Craig Dawson. The defender was initially adjudged to have made a clean challenge on the frontman, but following a VAR check, it was a clear foul and the visitors were awarded a penalty. Skipper Tielemans stepped up, however Fabiański saved the spot-kick and it remained 1-0 at half-time.
Twenty seconds into the second half, Benrahma darted inside from the left wing and shot straight at Ward. Leicester were absorbing the West Ham pressure, with Faes clearing Bowen's flick before it could test Ward. Introducing fresh legs into midfield, Rodgers made his second substitution of the match, as Wilfred Ndidi came on for Tielemans.
The Foxes remained compact in their defending, forcing the hosts into more long-range attempts. Souček guided a strike into the crowd while under pressure from 18 yards out. Rice headed a Cresswell corner in a similar direction as the match approached the hour mark.
A triple change, in City's final substitution window, meant Papy Mendy, Ayoze Pérez and Jamie Vardy would all be introduced in place of Dewsbury-Hall, Soumaré and Daka. All three were immediately into the action. Pérez slipped in Vardy, who was denied by Fabiański before Mendy sliced a follow-up off target.
After Rice had curled wide, City struck again for 2-0. Thomas intercepted Pablo Fornals' pass and found Pérez, who did brilliantly to play Barnes through. The Academy graduate raced in on goal, finishing first time past Fabiański for goal no.6 of the campaign. The 3,001 travelling fans were overjoyed in the away end, and set about serenading the Foxes up until the final whistle.
Leicester had a defensive job to do in the closing 10 minutes, as Ward tipped Rice's curler wide and then Benrahma lifted well over. Amartey's well-timed tackle stopped Gianluca Scamacca from finishing off Bowen's run and pass too. Into four minutes of added time, City remained impenetrable.
Major moment – Barnes breakaway
Having spurned the opportunity to double their advantage in the first half after Youri Tielemans was denied from 12 yards, it was Harvey Barnes who would add to James Maddison's eighth-minute opener with 12 minutes of normal time remaining.
Ayoze Pérez's beautiful pass into the feet of the No.7 was perfectly weighted, and he did the rest, slotting in to secure three Premier League points in London.
Who impressed – Physical Amartey
Speaking from the pressbox at London Stadium, 2000 League Cup winner Matt Elliott told LCFC Radio: "Daniel Amartey was strong and physical. In his defensive action, he was excellent. In a pairing with Wout Faes, I thought he was superb."
Where do we stand – 12th
City end their November action in 12th position in the Premier Leage table, with 17 points from 15 matches.
Coming up – MK Dons (A)
Leicester City's domestic action will pause for the winter break as the FIFA World Cup gets underway next weekend. They will play their next game during the week commencing 19 December, when they travel to stadium:mk for a Carabao Cup Fourth Round tie with MK Dons.