DAVID Nugent's first-half effort was enough to condemn the Clarets to a second home defeat in five games.
The former Burnley loanee had scored six times against his old club, and showed he had not lose the habit by flicking in his 12th of the season in the 31st minute.
The game had already got off to a bad start for Burnley as they lost Charlie Austin to injury inside the opening eight minutes.
The top scorer had been a doubt going into the game after being withdrawn early on Boxing Day due to a tight hamstring.
After passing a late fitness test he took a knock in the first minute and never recovered.
He was replaced by Martin Paterson, who had been dropped to the bench in favour of Keith Treacy, who was making his first league start for the Clarets since February.
Paterson, Danny Ings and Ross Wallace all had chances before Nugent put Leicester in front with his seventh goal against the club he joined on loan from Portsmouth during their Premier League season.
Ings fluffed a great chance to equalise when Wallace headed on Paterson's cross from the left before the break.
Paterson began the second half brightly and forced a couple of saves from Kasper Schmeichel.
Burnley looked livelier still when Sam Vokes came off the bench.
But that positive spell was shortlived and it needed the crossbar to deny Marko Futacs.
Paterson sent a volley straight at Schmeichel as time ran out, Leicester broke and Lee Grant did well to stop Ben Marshall from doubling their lead at the death.