Both sides started the new season with opening weekend victories but it was the Foxes who extended that run to top the early Barclays Premier League table on Saturday evening, as first-half goals from Shinji Okazaki and Riyad Mahrez were enough for a 2-1 win.
Slaven Bilic had seen his side impress in winning at Arsenal but tasted his first league defeat as manager of the Hammers, who reduced the deficit through Dimitri Payet's first goal for the club only to have goalkeeper Adrian sent off in the closing stages.
The hosts started positively enough and could have been ahead inside the opening two minutes as 16-year-old Reece Oxford, again trusted by Bilic to sit in front of his back four following an impressive outing at Arsenal, headed Dimitri Payet's deep free-kick on to the top of Kasper Schmeichel's crossbar.
Neither side fashioned another chance of note until past the midway point of the first half, with Mahrez, the star of last weekend's victory over Sunderland, forcing Adrian into his first meaningful action of the game as he easily danced past three defenders only to be met by the sprawling Spaniard.
However, Leicester were ahead just moments later as Jamie Vardy's cross evaded home defender Angelo Ogbonna and was met by Okazaki
His initial volley was acrobatically saved by Adrian but the Japan forward was on hand to head home the rebound and net his first goal for the club.
Vardy, who hit the headlines for all the wrong reasons earlier this week and was fined by the club after being filmed allegedly racially abusing a casino punter, was also pulling the strings and again linked up well with Okazaki to create the second.
This time the England international's flicked header picked out Okazaki, whose pass to Marc Albrighton allowed the winger to cut the ball back into the path of Mahrez, who made no mistake in slotting home his third of the season.
West Ham wanted a penalty on the stroke of half-time as Schmeichel and Diafra Sakho collided inside the Leicester box after the Senegal forward had poked the ball past the Foxes' goalkeeper, but referee Anthony Taylor was unmoved.
Bilic introduced Pedro Obiang at the break with Oxford making way and his side responded well, Payet pulling one back after his initial effort had been blocked into the path of Cheikhou Kouyate, who teed up the Frenchman to finish with aplomb.
Sakho had a chance to level on the hour-mark but his header from Mauro Zarate's corner was too close to Schmeichel, while Danny Drinkwater missed a great chance to wrap up the points with 15 minutes to go.
Schmeichel again denied Sakho after he combined with substitute Manuel Lanzini and, when Adrian was sent off in injury time for a high kick on Vardy after he trundled forward for a late corner, West Ham's poor afternoon came to an end.
Source : PA
Source: PA