Hull forced Birmingham goalkeeper Neil Etheridge into two important saves from Keane Lewis-Potter and Jacob Greaves, while Tom Eaves missed a sitter.
Birmingham’s only threats were lobs from Juninho Bacuna and Tahith Chong at either end of the second half, but both were comfortably held by Matt Ingram.
The visitors looked the more dangerous team for the first half hour and could have been ahead after 20 seconds.
Lewis-Potter got in behind Birmingham’s defence racing down the left to be presented with a one-on-one with Etheridge.
But the forward took an extra touch, driving himself even wider, and eventually his angled shot was blocked by the left leg of Etheridge.
Hull threatened again when Lewis-Potter teed up Greg Docherty 20 yards out but the midfielder’s low drive was deflected inches wide off Marc Roberts.
The visitors briefly appealed for a penalty when Eaves – making his 100th appearance for the Tigers – went down in a tussle with Roberts from George Honeyman’s cross, but referee Michael Salisbury waved play on.
Birmingham took a while to come into the game as an attacking force.
When they did, captain Gary Gardner looped a header comfortably over the bar from Roberts’ cross after climbing above Hull skipper Richard Smallwood.
Blues went closest to breaking the deadlock in the 39th minute.
Gardner flicked on Jordan Graham’s corner and Lyle Taylor diverted the ball goalwards only for goalkeeper Ingram to flip the ball away and Lewis-Potter hacked off the line.
Blues attempted to take a spectacular lead within 20 seconds of the restart, but Bacuna’s long-range lob was held by Ingram.
But Hull were again not ruthless enough in front of goal as another chance went begging.
Eaves opted to take a touch in front of goal rather than shoot from point-blank range and his shot was deflected the side-netting after Honeyman’s pull back.
The visitors remained on top and Blues had Etheridge to thank after the keeper darted off his line to deny clean-through Greaves.
Birmingham had little to show for their attacking efforts and a careless attempt by substitute Ryan Woods, which he sliced high and wide, summed up their afternoon in front of goal.
Then came Chong’s lob after he controlled Kristian Pedersen’s deep cross at the far post.
Defences were on top and in the end Hull will be disappointed they did not come away with three points, given they had the better chances.