The Blues opened the scoring through Matt Green's free header from a corner early in the first half before Andrew Shinnie capitalised on a mix-up between Allan McGregor and James Chester to double their lead two minutes after the break.
City mustered a spirited response in the final half hour of the contest at St Andrew's, reducing the deficit with Sone Aluko's 75th-minute penalty.
However, Steve Bruce's men were denied an equaliser when Darren Randolph kept out Nick Proschwitz's crisp low drive with three minutes remaining.
The Tigers never quite recovered from a lethargic opening. Green's header from Shane Ferguson's centre was avoidable and only as the first half wore on did the visitors find an attacking edge. A header from Robbie Brady, playing in behind Danny Graham, was as close as City came.
Their task became even harder when a lamentable lapse in concentration allowed Scott Allan to tee up Shinnie for a tap-in, but City almost produced a fight-back late on.
The impressive Aluko picked himself up from Paul Robinson's rash challenge to send Darren Randolph the wrong way from the spot. The Birmingham keeper had the last say, however, when pulling off a fine save to thwart Proschwitz from the edge of the box.
City could at least take heart from a first run-out for summer signing Maynor Figueroa, as well as a return to fitness for Stephen Quinn. Both players enjoyed 45 minutes in the first half and will hope to face Peterborough at London Road on Monday night.
New signing Yannick Sagbo, signed last night from Evian, must wait for international clearance before his debut.
Speaking after the game, Bruce said Sagbo was unlikely to get clearance in time to face Peterborough on Monday. The City boss also confirmed he would now switch his focus in the transfer market to central midfield.• Cameron Stewart is expected to find out on Monday whether he has damaged the knee that kept him out for eight months in 2011. The winger featured for a City XI at Grimsby last night.Birmingham
Darren Randolph, Neal Eardley, Hayden Mullins, Paul Robinson, Dan Burn, Shane Ferguson (Mitch Hancox 60), Tom Adeyemi (Wade Elliott 60), Scott Allan (Koby Arthur 60), Callum Reilly, Andrew Shinnie (Chris Burke 72), Matt Green
Subs: Colin Doyle, Oli Lee, Ryan Higgins
Hull City
Allan McGregor, James Chester, Curtis Davies (Alex Bruce 60), Maynor Figueroa (Paul McShane 46), Ahmed Elmohamady (Joe Dudgeon 60), George Boyd (Nick Proschwitz 60), Tom Cairney, Stephen Quinn (David Meyler 46), Robert Koren (Sone Aluko 46), Robbie Brady, Danny Graham (Matty Fryatt 60)
Subs: Steve Harper, Eldin Jakupovic
