QPR had to settle for a draw and are now without a win in six matches, having failed to score in their past three.
A stalemate was perhaps no surprise given that the two teams have the same number of wins and points as well as the same goal difference.
Rangers hoped the return of Lyndon Dykes after a thigh injury – and a switch to a 4-4-2 formation – would offer them more of a cutting edge up front.
But the Scotland striker struggled to make an impact before being substituted midway through the second half.
Bright Osayi-Samuel and Dykes both went close for the hosts seven minutes after the interval.
Ilias Chair pulled the ball back to Osayi-Samuel, whose right-footed shot was headed off the line by Birmingham captain Harlee Dean.
And from the resulting corner by Chair, Dykes’ header bounced up and clipped the top of the bar.
The visitors looked more threatening for much of the game and would have taken an early lead had Marc Roberts managed to connect with Gary Gardner’s ball in from the left.
Gardner sent a second-half volley narrowly wide, while Blues striker Scott Hogan twice netted from close range but both goals were rightly disallowed for offside.
Hogan was also denied by keeper Seny Dieng, who later dived to his left to push away a shot from Ivan Sunjic.
Osayi-Samuel tried to make things happen on a frustrating afternoon for QPR, who gave a first start to recent signing Albert Adomah.
Birmingham survived a late scare when Osayi-Samuel turned away from defender Kristian Pedersen only to shoot into the side netting.
Soon afterwards, QPR appealed in vain for a penalty after Osayi-Samuel went down under a challenge from Sunjic.
And with a couple of minutes remaining, Osayi-Samuel darted in from the right and teed up Chair, who fired wastefully wide of the far post.
Adomah was lively for parts of the first half, serving up a couple of decent crosses from the right flank, but he faded in the second and was replaced along with Dykes.
QPR: Dieng; Kakay, Dickie, Barbet, Wallace (Hamalainen 30); Osayi-Samuel, Cameron, Chair, Adomah (Willock 68) Bonne, Dykes (Ball 68).
Subs not used: Kelly, Masterson, Kane, Bettache.