Ayoze Perez scored a late own goal to condemn the Magpies to their sixth defeat in seven games.
Joselu opened the scoring for the North East side, Jacob Murphy played through Dwight Gayle who cut the ball back to the Spaniard for an easy finish.
Riyad Mahrez then equalised on 20 minutes with a left-footed drive from outside the area, too powerful for Karl Darlow who got a hand to it.
Leicester took the lead on the hour mark after Marc Albrighton set up Demarai Gray, who half-volleyed the ball via a deflection into the top left corner.
Dwight Gayle equalised after he fired the ball off Harry Maguire, which sent Kasper Schmeichel the wrong way and the ball into the bottom left corner.
Ayoze Perez poked home an unfortunate own goal four minutes from time after he tried to stop Shinji Okazaki having a strike on goal, giving Leicester the win.
The result leaves Newcastle 16th in the league table, only 2 points above the relegation zone.
Below are the Newcastle United player ratings following their narrow defeat against Leicester City…
