Leeds 1-0 Leicester
Luciano Becchio's third-minute penalty was enough to earn a second successive victory for Leeds at Elland Road.
Teenager Sam Byram was fouled inside the box by Jeff Schlupp after a neat bit of skill and Becchio sent Kasper Schmeichel the wrong way from the spot.
Former Leeds keeper Schmeichel denied them a second when he made a spectacular save from Paul Green.
Leicester dominated possession and went close when Martyn Waghorn hit the bar with a brilliant first-half strike.
The result follows up an impressive win over then-leaders Crystal Palace at the weekend.
A minute's applause was held before kick-off to commemorate the first anniversary of the death of former midfielder Gary Speed.
Within minutes, the impressive Byram caused the Foxes problems and drew the foul that earned the spot-kick despite a slight delay from referee Mick Russell.
After Becchio drilled in the penalty, Leicester's Waghorn flashed a shot across goal before grazing the top of the crossbar after pouncing on a loose ball in the box.
He went close again at the start of the second half, breaking clear before being crowded out as he failed to get in a shot on Leeds keeper Paddy Kenny.
Leicester struck the bar again late on when Schmeichel's long punt reared up on Kenny but the keeper watched it carefully as it bounced up wickedly.
Leeds manager Neil Warnock: "Gary would have loved that, us getting stuck in, I thought it was fitting.
"It was a Gary Speed game, roll your sleeves up and not shirking a tackle.
"We beat the top of the league on Saturday, but these (Leicester) are the best squad and you can tell that with the subs they made. But in both games we have deserved it.
"We played some good stuff, with flair, but also putting bodies on the line when we needed."
Leicester manager Nigel Pearson: "We lacked quality and did not play well, the first half in particular.
"You'll hear managers in this division talk about consistency and we were quite a way short of what is our best tonight.
"It was never going to be easy to come here, but I have no complaints. The nature of this league is that the sides which achieve consistency tend to finish in a strong position. We have done that for the most part, but not tonight."