Substitute Ben Marshall scored a late equaliser at St Andrew's as Birmingham failed to win for the fourth time in five league games.
The hosts went ahead on the stroke of half-time through Peter Lovenkrands after a cross by Marlon King.
And Birmingham looked set for their first home win since 18 September until Marshall levelled for new leaders Leicester with a shot in-off the post.
Jonathan Spector was sent off for the Blues in injury time.
The result ended Leicester's five-match winning run in the Championship.
But the Foxes will be relieved to have escaped with a point, despite being frustrated by 19-year-old England keeper Jack Butland in the first half.
The England international produced fine saves to deny Martyn Waghorn and Anthony Konockaert.
Blues see red
Jonathan Spector's dismissal means Birmingham have had players sent off in their last two league matches after substitute Nikola Zigic was also red carded in the 1-0 home defeat by Huddersfield on 6 October
Birmingham, who included Ravel Morrison from the start for the first time since August, took the lead against the run of play in first-half injury time as Lovenkrands converted a great cross from King for his third goal of the season.
Leicester keeper Kasper Schmeichel denied King when clean through yet time appeared to be running out for the visitors before Marshall drew the Foxes level out of nowhere in the 86th minute, his shot from distance going in off the inside of a post.
Spector was then dismissed as he was shown a second yellow card, while there was still time for Butland to produce another great stop to keep out Marshall's goalbound free-kick.
Leicester manager Nigel Pearson:
"Although we didn't start in the fashion we were expected to, the performance against Birmingham was an example of performing well.
"On balance I thought it was another fine team performance, but what pleases me most is the unity within the team and squad, and it is there for everyone to see.
"We showed some determination and quite a bit of composure to get something out of the game. They broke up the tempo very effectively but all in all my players dealt with the demands of the game very professionally."
Birmingham manager Lee Clark:
"My players showed a lot of passion, desire, drive and energy and I was hoping they could hold out, but unfortunately it was not to be.
Full Time The final whistle goes and the game is over.
Outswinging corner taken by Ben Marshall from the right by-line, clearance by David Murphy.
Indirect free kick taken by Ben Marshall.
90:00 +3:32 Dismissal
Dismissal Jonathan Spector sent from the field by the ref for foul and abusive language.
Free kick awarded for an unfair challenge on Ritchie De Laet by Jonathan Spector.
Unfair challenge on David Murphy by Jamie Vardy results in a free kick. Wade Elliott takes the indirect free kick.
Danny Drinkwater gives away a free kick for an unfair challenge on Leroy Lita. Jonathan Spector restarts play with the free kick.
85:59 Goal scored
Goal! - Ben Marshall - Birmingham 1 - 1 Leicester Ben Marshall gets on the score sheet with a goal from long distance to the bottom right corner of the goal. Birmingham 1-1 Leicester.
Free kick awarded for an unfair challenge on Keith Fahey by Marko Futacs. Free kick taken by Keith Fahey.
Substitution (Leicester) makes a substitution, with Marko Futacs coming on for Anthony Knockaert.
Corner taken by Ben Marshall, Jack Butland makes a save.
Substitution James Hurst goes off and Keith Fahey comes on.
Corner taken by Ben Marshall.
Ben Marshall takes a inswinging corner from the left by-line played to the near post, clearance made by Marlon King.
Substitution Jamie Vardy on for Martyn Waghorn.
Substitution Ben Marshall on for Lloyd Dyer.
The offside flag is raised against Andy King. Jack Butland restarts play with the free kick.
Anthony Knockaert takes the inswinging corner, clearance made by David Murphy.
David Murphy takes the free kick.
Booking The referee shows Martyn Waghorn a yellow card for unsporting behaviour.
Martyn Waghorn gives away a free kick for an unfair challenge on Jonathan Spector.
Nathan Redmond takes a short corner.
Kasper Schmeichel restarts play with the free kick.
Booking Ravel Morrison receives a caution.
Ravel Morrison gives away a free kick for an unfair challenge on Lloyd Dyer.
The referee blows for offside against David Nugent. Jack Butland restarts play with the free kick.
Substitution Leroy Lita joins the action as a substitute, replacing Peter Lovenkrands.
Shot from long distance by Martyn Waghorn goes over the bar. Inswinging corner taken left-footed by Anthony Knockaert from the right by-line.
Corner taken by Anthony Knockaert from the right by-line to the near post, Curtis Davies makes a clearance.
Foul by Wade Elliott on Anthony Knockaert, free kick awarded. Danny Drinkwater restarts play with the free kick.
Substitution Christopher Burke leaves the field to be replaced by Wade Elliott.
Anthony Knockaert takes a corner. Free kick awarded for a foul by Zak Whitbread on James Hurst. Jack Butland restarts play with the free kick.
Wes Morgan challenges Marlon King unfairly and gives away a free kick. Jonathan Spector takes the indirect free kick.
The referee blows for offside against David Nugent. Free kick taken by Jack Butland.
Free kick awarded for a foul by Danny Drinkwater on Ravel Morrison. Direct effort from the free kick comes in from Nathan Redmond.
Free kick awarded for a foul by Lloyd Dyer on James Hurst. Jack Butland takes the indirect free kick.
The second half begins.
45:00 +2:41 Half time
Half Time The match has reached half-time.
Assist on the goal came from Marlon King.
45:00 +1:07 Goal scored
Goal! - Peter Lovenkrands - Birmingham 1 - 0 Leicester A goal is scored by Peter Lovenkrands from close in to the bottom right corner of the goal. Birmingham 1-0 Leicester.
Free kick taken by James Hurst.
Booking Zak Whitbread receives a yellow card.
Zak Whitbread gives away a free kick for an unfair challenge on Ravel Morrison.
Anthony Knockaert takes a shot. Save by Jack Butland. Inswinging corner taken from the left by-line by Anthony Knockaert, Curtis Davies makes a clearance.
Inswinging corner taken by Lloyd Dyer from the left by-line.
The assistant referee flags for offside against Martyn Waghorn. Jack Butland takes the indirect free kick.
Christopher Burke produces a cross, clearance by Danny Drinkwater.
Inswinging corner taken from the left by-line by Nathan Redmond, clearance by Ritchie De Laet.
Wes Morgan concedes a free kick for a foul on Peter Lovenkrands. Indirect free kick taken by Peter Lovenkrands.
Nathan Redmond takes a shot. Kasper Schmeichel makes a save.
The offside flag is raised against David Nugent. Indirect free kick taken by David Murphy.
Christopher Burke concedes a free kick for a foul on Anthony Knockaert. Anthony Knockaert delivers the ball from the free kick left-footed from left wing.
Strike by Martyn Waghorn from inside the six-yard box clear the bar.
Unfair challenge on Andy King by Jonathan Spector results in a free kick. Danny Drinkwater takes the indirect free kick.
Shot by Andy King went wide of the left-hand upright.
Free kick awarded for an unfair challenge on Martyn Waghorn by David Murphy. Anthony Knockaert takes the indirect free kick.
Anthony Knockaert takes a shot. Save by Jack Butland.
Corner taken right-footed by Nathan Redmond from the right by-line, save by Kasper Schmeichel.
Curtis Davies gives away a free kick for an unfair challenge on Martyn Waghorn. Indirect free kick taken by Paul Konchesky. The offside flag is raised against Lloyd Dyer. Jack Butland takes the free kick.
Foul by James Hurst on Anthony Knockaert, free kick awarded. Indirect free kick taken by Paul Konchesky.
The offside flag is raised against Marlon King. Indirect free kick taken by Wes Morgan.
The assistant referee signals for offside against Martyn Waghorn. Jack Butland takes the indirect free kick.
Indirect free kick taken by Andy King.
Booking James Hurst goes into the referee's book for unsporting behaviour.
Unfair challenge on Paul Konchesky by James Hurst results in a free kick.
Foul by Lloyd Dyer on Ravel Morrison, free kick awarded. James Hurst restarts play with the free kick.
Lloyd Dyer is caught offside. Jack Butland restarts play with the free kick.
Anthony Knockaert takes the indirect free kick.
Booking Jonathan Spector is shown a yellow card.
Foul by Jonathan Spector on Anthony Knockaert, free kick awarded.
Nathan Redmond fouled by Danny Drinkwater, the ref awards a free kick. Indirect free kick taken by David Murphy.
Steven Caldwell gives away a free kick for an unfair challenge on David Nugent. Paul Konchesky takes the free kick.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.