Not many people gave Blues even a sniff of a chance going into this opening day encounter but come the final whistle Alex McLeish's men could count themselves mightily unlucky not to have come away with something.
The Premier League champions started the game well and pushed the visitors back but patience and hard work paid off and, in the main, Birmingham restricted United to long range chances only in the opening spells.
Clear-cut opportunities were at a premium in the first half but of those that came Blues had just as many as their world class opponents, James McFadden, Cameron Jerome and Franck Queudrue all coming close to scoring.
The only goal of the first half came from Wayne Rooney on 34 minutes and ultimately that was the strike that grabbed all three points.
But Sir Alex Ferguson will no doubt have breathed a sigh of relief on the final whistle because Blues were top drawer after the break and dominated the second half.
In what was a great showing of flowing football Keith Fahey, McFadden again and sub Christian Benitez all came mightily close to winning their side a point that no-one could have argued with.
Blues withstood United's early attacks well with a defence including debutants Roger Johnson and Gregory Vignal standing firm.
On eight minutes Joe Hart got down well to make a low save from Patrice Evra's fizzing shot before Dimitar Berbatov went down under a fair challenge from Stephen Carr just outside the box and referee Lee Mason waved play on.
The visitors first big chance came on ten minutes when McFadden crafted some space on the edge of the United penalty area, cut inside Jonny Evans and curled a low shot just wide of the target.
The game then swung back to the other end and frantic defending first from Lee Carsley to prevent Wayne Rooney and then keeper Hart to stop Nani kept the Red Devils at bay as they laid siege to the Blues goal.
On 12 minutes a trademark Rooney looped effort from 25 yards was palmed over the bar superbly by Hart as the hosts stepped on the gas.
Alex McLeish's charges played a 4-5-1 formation with Jerome the loan frontman and McFadden and Seb Larsson supporting from wide positions.
With 17 played McFadden marauded down the left and swung over a lovely low cross in the direction of the charging Jerome and Larsson, who had made great strides to get into the area. But United stopper Ben Foster had read it well and was quick off his line to claim.
Blues struggled to get out of their own halfway midway through the first period, but that's not to say they were completely under the cosh. In fact they restricted United only to shot from range, which Hart dealt with comfortably.
On 33 Fabio Da Silva burst past Vignal and whipped in a cross that rebounded off Hart's chest into the path of Rooney, whose instinctive shot deflected behind for a corner. After a couple of passes from the setpiece the ball was at the feet of Nani but the wideman shot first time instead of taking a touch first and completely missed the target.
But less than a minute later United did go in front. Nani broke down the left and crossed to the edge of the six-yard box for Rooney. The England striker's header hit Hart's left-hand post but rebounded kindly for the striker who slotted home at the second attempt.
With eight minutes to go until half-time Foster was left floundering on his line from a Jerome piledriver that flicked off Paul Scholes and flew just a couple of inches past the post. From the resulting Larsson corner Queudrue let fly with a spectacular header that was somehow cleared off the line by Nani with the keeper beaten once again.
Larsson's set-pieces were causing the home side problems inside their own area, one swinging effort into the box just before half-time caused particular havoc and led one United supporter sat in front of the press box to shout "Fergie, introduce the lads to one another at half-time".
An early contender for miss of the season came with the last kick of the half. Nani played in Evra down the left and he squared for Darren Fletcher who, six yards out, quite simply couldn't miss.
But miss he did in the form of a squirmed effort wide and the fact that the half ended only 1-0 rather than double that tally would no doubt have given the Blues players great heart.
Only one change was made at the start of the second half, Ryan Giggs replacing Nani.
Just seconds after the restart Rooney shot from range once again, this time about 30 yards, but Hart was Alert and flung himself to his right to push the ball behind with another top save.
On 50 Giggs was afforded too much space down the left and he floated over a cross that found Berbatov loitering with intent on the edge of the six yard box. Thankfully for Blues the Bulgarian tried the flash rather than the simply and his extravagant flick drifted wide.
A minute later Queudrue got a massively important headed touch on a Rooney cross. It was crucial because had the Frenchman not made contact then the ball would have fallen to the waiting Berbatov just behind him and he would surely have scored from close range.
With 58 played Blues broke and got plenty of men up to support Jerome. Larsson picked up possession on the right and laid a pass back to the onrushing Fahey, whose superbly hit daisycutter from 30 yard-plus flew narrowly past Foster's right-hand post.
On the hour mark Vignal up-ended Rooney just outside the area and picked up a yellow card for his troubles. Even more ominously, the free-kick was in prime Rooney territory. However the striker stepped away from the ball and left it for Giggs, who stepped up and curled it just over the bar.
On 64 Blues strung together a lovely, flowing passing move that started with Carsley and Ferguson and ended up with McFadden and Larsson exchanging a one-two, with the Scot bursting onto the edge of the area and letting fly with a low shot that was saved low down to his left by Foster.
Striker Garry O'Connor than came on in place of hard-working Jerome and took up the lone frontman mantle.
A minute later Giggs fouled Carr on the right 12 yards from the corner flag and McFadden's fizzing free-kick, whipped in towards goal, troubled Foster who could do nothing else except punch to the edge of his area.
Blues were putting in an excellent showing, enjoying more of the ball and stringing together some good moves - in no way daunted by the Premier League champions or the arena in which they were playing.
Berbatov's header was cleared off the line superbly by Carr on 71 before, at the other end, Foster was forced to claw away another Larsson cross. The visitors were causing their esteemed hosts problems.
Ecuadorian frontman Christian Benitez was introduced to the action, for his debut, three minutes later in place of Carsley as McLeish decided to really go for it. And why not, with his side having dominated large parts of the second half.
Fletcher became the second player to be booked for a foul on Fahey on 75.
Then, three minutes later, Queudrue released Benitez with a long range pass. The striker beat Wes Brown hands down, cutting back inside the United defender, before unleashing an angled drive that looked destined for the back of the net until Foster flung himself to his left and pushed the ball away with his fingertips.
On 81 there was a great moment for 21-year-old winger James O'Shea. Signed only a week ago from Irish side Galway United the right-sided player got to make his Blues bow at the Theatre of Dreams, coming on for Larsson.
Rooney headed wide a Giggs cross on 84 and Michael Owen got in behind the visiting defence in injury time and saw a shot saved by Hart but in truth had either chance gone in a 2-0 scoreline would have flattered United.
Despite the narrow defeat, a truly impressive showing against one of the world's best sides will no doubt stand Blues in good stead for the rest of the Premier League campaign.
Man Utd: Ben Foster, Fabio Da Silva, John O'Shea (c), Jonathan Evans (Wes Brown 75), Patrice Evra, Antonio Valencia, Darren Fletcher, Paul Scholes, Nani (Ryan Giggs 46), Dimitar Berbatov (Michael Owen 75), Wayne Rooney. Unused subs: Tomasz Kuszczak (gk), Anderson, Darren Gibson, Richie De Laet.
Goals: Rooney (34)
Blues: Joe Hart, Stephen Carr, Roger Johnson, Franck Queudrue, Gregory Vignal, Sebastian Larsson (James O'Shea 81), Barry Ferguson, Lee Carsley (Christian Benitez 74), Keith Fahey, James McFadden, Cameron Jerome (Garry O'Connor 65). Unused subs: Maik Taylor (gk), Kevin Phillips, Gary McSheffrey, Stuart Parnaby.
Referee: Lee Mason
Attendance: 75,062
