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."
Live Text Commentary
Full Time The game is over, as the referee blows his whistle.90:00 +3:47
Danny Drinkwater produces a volleyed right-footed shot from 25 yards. Tom Lees gets a block in.90:00 +3:00
Inswinging corner taken by Danny Drinkwater, clearance by Michael Brown.90:00 +0:09
Unfair challenge on Danny Drinkwater by Luciano Becchio results in a free kick. Kasper Schmeichel takes the free kick.88:33
Free kick awarded for an unfair challenge on David Norris by Anthony Knockaert. Direct free kick taken by Patrick Kenny.87:11
Shot by David Norris from outside the box goes high over the crossbar.86:17
Andy King fouled by David Norris, the ref awards a free kick. Free kick crossed left-footed by Anthony Knockaert from right channel, Alan Tate manages to make a clearance.84:41
Foul by Danny Drinkwater on Michael Brown, free kick awarded. Direct free kick taken by Patrick Kenny.84:14
The assistant referee flags for offside against Luciano Becchio. Kasper Schmeichel restarts play with the free kick.83:34
Danny Drinkwater gives away a free kick for an unfair challenge on Michael Brown. Free kick taken by Patrick Kenny.82:50
Luciano Becchio is flagged offside by the assistant referee. Kasper Schmeichel takes the free kick.80:45
The offside flag is raised against Lloyd Dyer. Patrick Kenny takes the indirect free kick.80:15
The ball is swung over by Ritchie De Laet.78:27
Free kick awarded for a foul by Marko Futacs on Lee Peltier. Direct free kick taken by Patrick Kenny.76:21 Substitution
Substitution Martyn Waghorn goes off and Jesse Lingard comes on.76:21
Effort from the edge of the area by Marko Futacs goes wide of the right-hand upright.75:38
Lee Peltier concedes a free kick for a foul on Marko Futacs. Direct free kick taken by Danny Drinkwater.69:12
The ball is crossed by Jeff Schlupp, Alan Tate manages to make a clearance.68:42
Luciano Becchio is flagged offside by the assistant referee. Kasper Schmeichel restarts play with the free kick.68:16
Foul by Wes Morgan on Luciano Becchio, free kick awarded. Lee Peltier takes the direct free kick.
Samuel Byram concedes a free kick for a foul on Lloyd Dyer. Free kick taken by Zak Whitbread.65:47
The offside flag is raised against Marko Futacs. Patrick Kenny restarts play with the free kick.65:03
Michael Brown produces a left-footed shot from just outside the penalty box that goes wide left of the target.63:42
Michael Tonge delivers the ball, clearance by Ritchie De Laet. Corner taken right-footed by Michael Tonge from the left by-line, Wes Morgan manages to make a clearance.56:10
The official flags El-Hadji Diouf offside. Kasper Schmeichel takes the free kick.56:10 Substitution
Substitution Michael Brown comes on in place of Jerome Thomas.56:10
Shot by Martyn Waghorn from outside the box goes over the net. Shot from 30 yards by Anthony Knockaert. Patrick Kenny makes a save. Martyn Waghorn takes a outswinging corner from the left by-line to the near post, clearance made by Luciano Becchio.56:10 Substitution
Substitution Anthony Knockaert replaces Ben Marshall.56:10 Substitution
Substitution (Leicester) makes a substitution, with Marko Futacs coming on for Jamie Vardy.55:37
Jerome Thomas has an effort at goal from just inside the box that misses to the right of the target.54:56
Unfair challenge on Luciano Becchio by Martyn Waghorn results in a free kick. El-Hadji Diouf restarts play with the free kick.53:47
Foul by Luciano Becchio on Danny Drinkwater, free kick awarded. Martyn Waghorn crosses the ball, Wes Morgan takes a shot. Patrick Kenny makes a comfortable save.51:50
Corner taken by El-Hadji Diouf from the left by-line, Wes Morgan makes a clearance.50:37
Free kick crossed right-footed by El-Hadji Diouf, Tom Lees makes a clearance.50:37 Booking
Booking Ritchie De Laet is shown a yellow card for unsporting behaviour.50:15
Jerome Thomas fouled by Ritchie De Laet, the ref awards a free kick.47:50
Short corner worked by Martyn Waghorn.45:01
The second half kicks off.45:00 +1:06 Half time
Half Time It is the end of the first-half.45:00 +0:06
Zak Whitbread challenges El-Hadji Diouf unfairly and gives away a free kick. Direct free kick taken by Patrick Kenny.44:31
The referee blows for offside. Free kick taken by Kasper Schmeichel.43:20
Andy King takes a shot. Alan Tate gets a block in. Jamie Vardy has an effort at goal from the edge of the area that misses to the right of the target.41:08
Andy King fouled by David Norris, the ref awards a free kick. Ritchie De Laet takes the direct free kick.40:41
A cross is delivered by Paul Green, Kasper Schmeichel makes a save.39:36
The ball is sent over by Ritchie De Laet, Lloyd Dyer takes a shot. Patrick Kenny makes a comfortable save.37:06
The ball is delivered by Jeff Schlupp, clearance by Tom Lees.36:19
The assistant referee signals for offside against Jerome Thomas. Kasper Schmeichel restarts play with the free kick.34:55
The official flags Luciano Becchio offside. Indirect free kick taken by Kasper Schmeichel.33:42
Martyn Waghorn has an effort at goal. Comfortable save by Patrick Kenny.32:28
Centre by Ben Marshall. Shot from 12 yards from Martyn Waghorn.30:55
The ball is crossed by Ritchie De Laet, clearance by Alan Tate. Corner taken right-footed by Ben Marshall, clearance by Tom Lees.30:01
Michael Tonge concedes a free kick for a foul on Jamie Vardy. Direct free kick taken by Zak Whitbread.28:03
Ritchie De Laet concedes a free kick for a foul on Jerome Thomas. El-Hadji Diouf crosses the ball from the free kick right-footed from left wing, Kasper Schmeichel makes a save.26:29
The ball is crossed by Luciano Becchio, Shot by Paul Green. Save by Kasper Schmeichel. El-Hadji Diouf takes a inswinging corner from the left by-line played to the near post, Zak Whitbread manages to make a clearance.25:15
El-Hadji Diouf takes the outswinging corner, Header by Tom Lees from deep inside the penalty area misses to the right of the target.18:55
Foul by Samuel Byram on Danny Drinkwater, free kick awarded. Direct free kick taken by Jeff Schlupp.13:22
Corner taken right-footed by El-Hadji Diouf from the left by-line to the near post, clearance made by Wes Morgan. A cross is delivered by Samuel Byram. Tom Lees concedes a free kick for a foul on Martyn Waghorn. Ben Marshall has an effort direct from the free kick, blocked by David Norris.12:42
Effort on goal by Ritchie De Laet from 20 yards. Save by Patrick Kenny.11:53
Outswinging corner taken by El-Hadji Diouf, clearance made by Lloyd Dyer.11:04
The referee blows for offside against Lee Peltier. Kasper Schmeichel restarts play with the free kick.10:38
David Norris is caught offside. Kasper Schmeichel takes the free kick.8:32
Foul by Zak Whitbread on Luciano Becchio, free kick awarded. Tom Lees restarts play with the free kick.6:46
Paul Green delivers the ball, clearance by Zak Whitbread.4:29
Inswinging corner taken from the right by-line by Andy King, Samuel Byram manages to make a clearance.2:49
Assist by Samuel Byram.2:49 Goal scored
Goal! - Luciano Becchio - Leeds 1 - 0 Leicester Penalty taken left-footed by Luciano Becchio and scored. Leeds 1-0 Leicester.1:38
Jeff Schlupp concedes a Penalty for a foul on Samuel Byram.0:47
Corner taken right-footed by El-Hadji Diouf from the left by-line, Danny Drinkwater makes a clearance.0:00
The referee gets the game started.
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