Kasper Schmeichel's injury-time penalty save helped Leicester move up to second place in the Championship as a David Nugent strike saw off Middlesbrough.
Leicester hit the woodwork four times before ex-England international Nugent met a flick-on from strike partner Chris Wood with a crisp half-volley.
Anthony Knockaert's drive hit the bar and then post, while the Boro frame also denied Michael Keane and Wood.
Schmeichel kept out Marvin Emnes' penalty as the visitors remained fifth.
Pearson's Boro past
Leicester boss Nigel Pearson remains a cult hero at Middlesbrough after captaining the Teesside club to Premier League promotion and two Wembley cup finals in the 1990s.
The Dane flung himself low to his left to push away the substitute's effort and cap a miserable day for Tony Mowbray's men.
The game was delayed by 15 minutes after the Middlesbrough players and staff were forced to walk the final part of their journey to the King Power Stadium because of heavy traffic in snowy weather.
But the less than ideal preparation did not seem to affect the visitors as they more than matched the in-form hosts during an entertaining first-half.
Leicester had won their previous three league games going into the match, scoring 11 goals in the process, and both teams knew they would move into the automatic promotion places with a victory.
Middlesbrough enjoyed plenty of attacking possession in the opening hour, though their goal also led a charmed life as the Foxes hit the woodwork on three occasions.
Knockaert hit a thunderous strike that beat Boro keeper Jason Steele but the ball hit the underside of the crossbar and bounced on the goalline before striking the right-hand post.
Leicester boast the meanest defence in the Championship having conceded just 23 goals in their opening 28 matches.
Keane's header looped on to the away crossbar in first-half stoppage time before Wood, who has scored six goals in three Leicester appearances since joining in a £1m deal from West Bromwich Albion, hit the woodwork with a far-post header.
But Middlesbrough could have opened the scoring after 36 minutes when Paul Konchesky blocked Rhys Williams's pullback from a tight angle after the away skipper had rounded Schmeichel.
Schmeichel denied the visitors again seconds later when he smartly blocked Andre Bikey's close-range header, but his finest stop came in the second minute of added time.
Foxes substitute Jamie Vardy inexplicably hacked down Williams, giving Emnes the opportunity to move Boro into fourth, but Schmeichel ensured Leicester kept their fifth clean sheet in six league matches.
Leicester manager Nigel Pearson:
"It feels great to be second in the league. The players applied themselves well tonight.
"In the second half we pushed the full-backs forward more and took more chances going forward.
"I think we had the better chances and it was a good game."
Middlesbrough manager Tony Mowbray:
"I'm unbelievably disappointed - I thought we did enough not to lose the game. We created more than enough chances to get something from the game against a good Leicester side who have been scoring freely.
"But we didn't stick the ball in the back of the net and goals change games."
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