Watford substitute Craig Forsyth struck 10 minutes from time to to extend the Hornets' unbeaten run to four games.
Adrian Mariappa headed Watford into a fifth-minute lead, but Leicester recovered with two goals in seven minutes from striker David Nugent.
A deflected free-kick from Sean Murray made it level in the 34th minute.
The Foxes dominated the second half but Forysth scored against the run of play before Watford's Lloyd Doyley was sent off in injury time.
Watford manager Sean Dyche made his first change in four games with Troy Deeney missing out because of a hamstring injury.
But it did not seem to upset his side, who grabbed an early lead when highly-rated defender Mariappa headed the opener, powering home Murray's free-kick.
Joe Garner could have doubled their lead but was denied well by keeper Kasper Schmeichel before Leicester broke to the other end to equalise in the 12th minute.
Former England striker Nugent was fed by Jermaine Beckford before cutting inside to fire a low shot into the bottom corner.
Seven minutes later, Beckford teed up Nugent again and his strike partner smashed a fierce strike past Scott Loach.
Watford were back on terms after Matt Mills brought down Alex Kacaniklic on the edge of the box and teenager Murray stepped up to score his first senior goal, with the aid of a deflection that deceived Schmeichel.
Leicester wasted a number of golden chances to regain the lead, defender Wes Morgan and Beckford heading wastefully off target.
Loach then spilled a Beckford shot, but Nugent could not react in time to grab his hat-trick.
And they were made to pay when a raking pass from John Eustace picked out Forsyth, who rifled the ball past Schmeichel.
Leicester's Richie Wellens almost levelled again but blasted over with five minutes to go, before Lloyd Doyley picked up a red card for hauling down Beckford as he raced in on goal.
Watford boss Sean Dyche: "It was a great win against a very powerful squad, let alone side, that have been put together for multi-millions.
"We knew it would be a tough task and it was sure to be with a couple of quality finishes but out lads have built a great resolve.
"The feel of the team and the fans here and their connection is really important to what we do and it was a good night for all."
Leicester boss Nigel Pearson: "We need to be better and more efficient and more consistent - simple as that.
"The goals that we conceded were poor goals. We didn't start the game well enough, scored two exceptionally good goals and that should be enough to win the game but we've made some poor decisions on the night and it's cost us dearly.
"We know their style of play, they do it very well, but when we played football in their half we caused them all sorts of problems."
- 01 Loach
- 02 Hodson
- 06 Mariappa
- 12 Doyley Dismissed
- 33 Nosworthy
- 04 Eustace
- 18 Kacaniklic (Dickinson - 90' )
- 22 Murray (Forsyth - 46' )
- 32 Hogg
- 10 Iwelumo
- 25 Garner Booked (Buaben - 82' )
- 13 Gilmartin
- 03 Dickinson
- 07 Yeates
- 11 Forsyth
- 19 Buaben
- 01 Schmeichel
- 02 Peltier (Morgan - 46' )
- 03 Konchesky Booked
- 05 Mills Booked
- 12 St. Ledger
- 11 Dyer (Howard - 84' )
- 16 Drinkwater (Danns - 46' )
- 19 Wellens
- 07 Gallagher
- 20 Beckford
- 35 Nugent
- 25 Logan
- 26 Morgan
- 23 Danns
- 09 Howard
- 22 Marshall
Live Text Commentary
Full Time The final whistle is blown by the referee.90:00 +4:50
Foul by Wes Morgan on Chris Iwelumo, free kick awarded. John Eustace restarts play with the free kick.90:00 +1:45
Paul Gallagher fires a strike on goal direct from the free kick.90:00 +1:45 Substitution
Substitution Carl Dickinson replaces Alex Kacaniklic.90:00 +1:45 Dismissal
Dismissal Lloyd Doyley shown a red card.90:00 +1:02
Free kick awarded for a foul by Lloyd Doyley on Jermaine Beckford.90:00 +0:18
The ball is sent over by Paul Konchesky, Header by Sean St. Ledger from deep inside the penalty area misses to the right of the target.88:21
Free kick awarded for a foul by Paul Gallagher on John Eustace. Adrian Mariappa takes the direct free kick.87:28
Free kick awarded for a foul by Alex Kacaniklic on Paul Gallagher. Direct free kick taken by Kasper Schmeichel.86:24
Effort on goal by Richie Wellens from just inside the area clears the bar.85:54
Foul by Craig Forsyth on Sean St. Ledger, free kick awarded. Free kick crossed right-footed by Paul Gallagher from right by-line, Scott Loach makes a save.85:43
Paul Konchesky crosses the ball.83:49
Kasper Schmeichel restarts play with the free kick.83:49 Substitution
Substitution Steve Howard is brought on as a substitute for Lloyd Dyer.83:49
Chris Iwelumo challenges Richie Wellens unfairly and gives away a free kick.81:48
Kasper Schmeichel takes the free kick.81:48 Substitution
Substitution Prince Buaben replaces Joe Garner.81:48
Joe Garner gives away a free kick for an unfair challenge on Matt Mills.79:47 Goal scored
Goal! - Craig Forsyth - Watford 3 - 2 Leicester Craig Forsyth grabs a goal from the edge of the area to the bottom right corner of the goal. Watford 3-2 Leicester.78:55
Richie Wellens challenges John Eustace unfairly and gives away a free kick. Scott Loach restarts play with the free kick.
Outswinging corner taken right-footed by Paul Gallagher played to the near post, Nyron Nosworthy makes a clearance.77:34
Corner from right by-line taken by Alex Kacaniklic.77:17
Shot by John Eustace. Kasper Schmeichel makes a save.76:42
The referee blows for offside against Chris Iwelumo. Paul Gallagher takes the indirect free kick.75:23
Neil Danns fouled by Chris Iwelumo, the ref awards a free kick. Paul Konchesky restarts play with the free kick.74:51
Effort from just outside the box by Paul Konchesky goes over the bar.74:43
Paul Gallagher sends in a cross, clearance by Adrian Mariappa.73:49
Paul Gallagher produces a cross.73:21
Foul by Jonathan Hogg on Neil Danns, free kick awarded. Direct free kick taken by Paul Gallagher.71:45
Paul Gallagher takes a inswinging corner from the left by-line played to the near post, Joe Garner makes a clearance.71:32
A cross is delivered by Sean St. Ledger, John Eustace makes a clearance.69:28
Corner taken right-footed by Paul Gallagher from the left by-line, Wes Morgan has a headed effort at goal from close range which goes wide left of the target.69:10
Paul Gallagher takes a shot. Save by Scott Loach.69:00
Lloyd Dyer delivers the ball, Adrian Mariappa makes a clearance.65:24
Corner taken left-footed by Alex Kacaniklic from the right by-line to the near post, clearance by Neil Danns.65:10
The ball is sent over by Alex Kacaniklic, save by Kasper Schmeichel.62:54
Corner taken left-footed by Alex Kacaniklic from the left by-line, Jonathan Hogg takes a shot from inside the box clearing the bar.61:52
Free kick taken by Alex Kacaniklic.61:52 Booking
Booking Paul Konchesky is given a yellow card.61:43
Unfair challenge on Alex Kacaniklic by Paul Konchesky results in a free kick.59:32
Paul Gallagher produces a cross, Nyron Nosworthy makes a clearance.57:41
Jermaine Beckford takes a shot. Save by Scott Loach.56:05
Lee Hodson crosses the ball, save by Kasper Schmeichel.54:00
Unfair challenge on Sean St. Ledger by Chris Iwelumo results in a free kick. Direct free kick taken by Matt Mills.53:02
The ball is sent over by Sean St. Ledger, Jermaine Beckford has a headed effort at goal from close in which goes wide right of the goal.52:10
Joe Garner produces a right-footed shot from the edge of the box and misses to the left of the target.52:03
The ball is swung over by Craig Forsyth, clearance by Wes Morgan.50:38
Neil Danns sends in a cross.49:33
Free kick awarded for a foul by John Eustace on Sean St. Ledger. Free kick crossed by Paul Gallagher, clearance made by Craig Forsyth.48:19
Free kick awarded for an unfair challenge on David Nugent by Lloyd Doyley. Paul Gallagher delivers the ball from the free kick right-footed from right channel, clearance by Nyron Nosworthy.46:30
Corner taken by Paul Konchesky played to the near post, clearance by John Eustace.46:22
A cross is delivered by Paul Gallagher, clearance made by Jonathan Hogg.45:01
The referee gets the second half started.45:01 Substitution
Substitution Craig Forsyth joins the action as a substitute, replacing Sean Murray.45:01 Substitution
Substitution Neil Danns replaces Daniel Drinkwater.45:01 Substitution
Substitution Wes Morgan is brought on as a substitute for Lee Peltier.45:00 +4:08 Half time
Half Time The ref blows to end the first period.45:00 +3:32
Outswinging corner taken right-footed by Paul Gallagher, Chris Iwelumo manages to make a clearance.45:00 +2:15
Centre by Lee Hodson, Sean St. Ledger manages to make a clearance.45:00 +0:14
Daniel Drinkwater challenges Joe Garner unfairly and gives away a free kick. Scott Loach restarts play with the free kick.42:38
Paul Gallagher takes a shot. Joe Garner gets a block in.42:11
Lee Peltier sends in a cross.40:26
Shot from just outside the penalty area by Sean Murray misses to the left of the target.39:41
Free kick awarded for an unfair challenge on Sean St. Ledger by Chris Iwelumo. Free kick taken by Richie Wellens.39:13
Shot from just outside the box by Daniel Drinkwater goes over the bar.38:41
Paul Gallagher takes the outswinging corner, clearance made by Nyron Nosworthy.38:33
The ball is delivered by Paul Gallagher, blocked by Lloyd Doyley.37:24
The ball is crossed by Paul Gallagher, save by Scott Loach.35:46
Foul by Nyron Nosworthy on Jermaine Beckford, free kick awarded. Free kick taken by Paul Konchesky.35:28
Lee Hodson delivers the ball, Kasper Schmeichel makes a save.34:06
Chris Iwelumo is flagged offside by the assistant referee. Kasper Schmeichel restarts play with the free kick.32:45 Goal scored
Goal! - Sean Murray - Watford 2 - 2 Leicester Free kick scored by Sean Murray from long distance to the bottom right corner of the goal. Watford 2-2 Leicester.31:51 Booking
Booking Matt Mills receives a yellow card for unsporting behaviour.31:30
Free kick awarded for an unfair challenge on Alex Kacaniklic by Matt Mills.29:44
The ball is swung over by Lloyd Dyer, Jermaine Beckford takes a shot. Nyron Nosworthy gets a block in.26:34
The referee blows for offside. Indirect free kick taken by Kasper Schmeichel.24:40
Sean Murray sends in a cross.22:30
The ball is delivered by Lloyd Dyer, Effort on goal by David Nugent from deep inside the penalty area misses to the right of the goal.22:12
The ball is sent over by Lloyd Dyer, clearance made by Lloyd Doyley.21:29
Free kick awarded for an unfair challenge on Richie Wellens by Jonathan Hogg. Richie Wellens takes the free kick.20:46
The ball is swung over by Paul Gallagher.20:02
Shot from just outside the penalty area by Daniel Drinkwater misses to the left of the target.18:29
The referee blows for offside against Chris Iwelumo. Indirect free kick taken by Kasper Schmeichel.17:15
Assist on the goal came from Jermaine Beckford.17:15 Goal scored
Goal! - David Nugent - Watford 1 - 2 Leicester David Nugent finds the net with a goal from the edge of the penalty box to the top left corner of the goal. Watford 1-2 Leicester.16:27
Jonathan Hogg takes a shot. Blocked by Matt Mills. Close range shot by Alex Kacaniklic goes over the bar.13:53
Strike comes in from Paul Gallagher from the free kick.13:53 Booking
Booking Booking for Joe Garner for unsporting behaviour.13:48
Jermaine Beckford fouled by Joe Garner, the ref awards a free kick.13:00
Alex Kacaniklic sends in a cross, Lee Peltier makes a clearance.11:57
Lee Hodson sends in a cross, clearance by Lee Peltier.11:08
Sean Murray takes the inswinging corner, save made by Kasper Schmeichel.10:01 Goal scored
Goal! - David Nugent - Watford 1 - 1 Leicester Goal scored by David Nugent from just outside the area to the bottom right corner of the goal. Watford 1-1 Leicester.9:29
Corner taken by Sean Murray played to the near post, save by Kasper Schmeichel.8:58
Corner taken right-footed by Sean Murray, clearance made by Richie Wellens.7:30
Adrian Mariappa challenges Jermaine Beckford unfairly and gives away a free kick. Lee Peltier restarts play with the free kick.4:37
The assist for the goal came from Sean Murray.4:37 Goal scored
Goal! - Adrian Mariappa - Watford 1 - 0 Leicester Adrian Mariappa finds the net with a headed goal from close in. Watford 1-0 Leicester.3:51
Lee Peltier challenges Joe Garner unfairly and gives away a free kick. Sean Murray crosses the ball,0:00
The ref blows the whistle to start the match.
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