The visitors had led in the first half when David Davis reacted fastest to tuck in the rebound after Adam Bogdan saved Clayton Donaldson's penalty.
Earlier, Donaldson had hit the post for Blues, and David Cotterill nearly made it 2-0 after half-time but hit the bar.
Wigan went close through Nick Powell before Davies turned in from close range, but the Blues remain unbeaten.
Despite Wigan controlling possession, Birmingham created the better chances and could have gone ahead when Jacques Maghoma's shot was palmed out by Bogdan into the path of the on-rushing Donaldson, but the Jamaican's instinctive effort struck the woodwork.
After the Wigan keeper brought Donaldson down in the area, he got down low to save the striker's resultant spot-kick but Davis was too quick to the rebound and coolly finished.
Powell was then denied by Birmingham stopper Tomasz Kuszczak after half-time and the Blues looked set for their second away win in four days, before Davies' late leveller.
The result leaves Blues one point above the Latics in the table and without a defeat in seven league games, having drawn six of them.
Wigan manager Gary Caldwell:
"There was one team that tried to win it. They got gifted a goal from not our doing and we had to chase a game against a team that likes to pack the defence and counter attack which is never easy. I thought we controlled the situation really well and if anything deserved to win the game so it's a bit of frustration."
"The rule is you can't go in the box until the ball's hit, it's clear. I would just like them to own it up at times to say 'I've made a mistake'. It would help.
"It's the sheer defiance that there's nothing wrong when really there is something wrong. A goal could have been avoided. I felt he was marginally offside as well. You can't get that many things wrong in a football match as important as this."
Birmingham City manager Gary Rowett:
"I couldn't see it, I wish he had (encroached) because I'm sure Clayton would have scored with the retaken one.
"Eight weeks ago the goalkeeper would have been sent off but now it's the double jeopardy rules. A point I think was a fair reflection of the game. They are a good side Wigan, I think they'll have a good season. I'm sure.
"I'm quite enthused at the start. There will be a lot of teams that will panicking a little bit after three games and wondering what work they need to do in the final few weeks of the transfer window. I'm quite pleased with the way we've started the season."
Match ends, Wigan Athletic 1, Birmingham City 1.
Second Half ends, Wigan Athletic 1, Birmingham City 1.
Attempt missed. Yanic Wildschut (Wigan Athletic) right footed shot from outside the box misses to the right. Assisted by Dan Burn with a headed pass.
Corner,  Wigan Athletic. Conceded by Greg Stewart.
Shaun MacDonald (Wigan Athletic) wins a free kick in the defensive half.
Foul by Clayton Donaldson (Birmingham City).
Attempt missed. Dan Burn (Wigan Athletic) header from the right side of the six yard box is high and wide to the right. Assisted by Michael Jacobs with a cross following a corner.
Jonathan Grounds (Birmingham City) is shown the yellow card.
Corner,  Wigan Athletic. Conceded by Tomasz Kuszczak.
Attempt saved. Michael Jacobs (Wigan Athletic) right footed shot from the centre of the box is saved in the top left corner. Assisted by Craig Davies.
Shaun MacDonald (Wigan Athletic) wins a free kick in the defensive half.
Foul by Jonathan Grounds (Birmingham City).
Foul by Alex Gilbey (Wigan Athletic).
Greg Stewart (Birmingham City) wins a free kick on the left wing.
Foul by Michael Jacobs (Wigan Athletic).
Greg Stewart (Birmingham City) wins a free kick in the defensive half.
Goal!  Wigan Athletic 1, Birmingham City 1. Craig Davies (Wigan Athletic) right footed shot from very close range to the high centre of the goal. Assisted by William Grigg.
Foul by William Grigg (Wigan Athletic).
Ryan Shotton (Birmingham City) wins a free kick in the defensive half.
Foul by Stephen Warnock (Wigan Athletic).
Maikel Kieftenbeld (Birmingham City) wins a free kick in the defensive half.
Offside, Birmingham City. Maikel Kieftenbeld tries a through ball, but Che Adams is caught offside.
Corner,  Wigan Athletic. Conceded by Jonathan Spector.
Substitution, Wigan Athletic. Craig Davies replaces Max Power.
Substitution, Birmingham City. Viv Solomon-Otabor replaces Jacques Maghoma.
Substitution, Birmingham City. Greg Stewart replaces David Davis.
Attempt blocked. Nick Powell (Wigan Athletic) left footed shot from outside the box is blocked. Assisted by Shaun MacDonald.
Attempt blocked. Maikel Kieftenbeld (Birmingham City) right footed shot from outside the box is blocked.
Attempt blocked. Nick Powell (Wigan Athletic) right footed shot from the right side of the box is blocked.
Attempt blocked. Nick Powell (Wigan Athletic) right footed shot from outside the box is blocked.
Corner,  Wigan Athletic. Conceded by Stephen Gleeson.
Michael Jacobs (Wigan Athletic) wins a free kick in the defensive half.
Foul by Jacques Maghoma (Birmingham City).
Offside, Birmingham City. Jacques Maghoma tries a through ball, but Che Adams is caught offside.
Clayton Donaldson (Birmingham City) is shown the yellow card for a bad foul.
Stephen Warnock (Wigan Athletic) wins a free kick on the left wing.
Foul by Clayton Donaldson (Birmingham City).
Attempt blocked. Nick Powell (Wigan Athletic) right footed shot from outside the box is blocked.
Corner,  Birmingham City. Conceded by Dan Burn.
Substitution, Birmingham City. Che Adams replaces David Cotterill.
Wigan Athletic rescued a late point through Craig Davies to deny Birmingham City a second consecutive victory.