Snow and wind hampered the eagerly-anticipated encounter, with the largely uninspiring stalemate leaving second-placed Saints four points adrift of npower Championship leaders West Ham and Blues, in fifth, five points off the automatic promotion places with a game in hand.
Guirane N'Daw's early header proved the closest chance of a first half in which Birmingham started strongly but the visitors went on to dominate.
Marlon King forced a super save at the start of the second period from Kelvin Davis, who produced another solid stop to keep out N'Daw soon after and deny a City side who went on to shade proceedings.
Saints failed to force a single stop from Boaz Myhill at the other end and survived the 83rd-minute dismissal of defender Danny Fox for a second bookable offence, but they will highly value the point despite now having won just two of their last 10 league games after a barnstorming start.
Blues, who remain unbeaten in the league at St Andrew's this term, saw their six-match winning sequence come to an end but are unbeaten in 11.
Nikola Zigic failed a fitness test on the knee injury sustained in the process of bagging his fourth goal in Tuesday's 4-1 triumph at Leeds, fit-again top scorer King coming in as a suitable replacement as one of three changes.
Birmingham started in the ascendancy and no-nonsense midfielder N'Daw, back in the fold after his African Nations Cup campaign was brought to a premature end with Senegal, headed narrowly wide after eight minutes.
The home side certainly started the brighter but Saints boss Nigel Adkins, who named an unchanged line-up, adapted his side's shape to add an extra man in midfield and the visitors gained a foothold on the encounter.
Five corners highlighted their new-found dominance but City stopper Myhill, likewise counterpart Davis, was still to make a save as the half-hour mark passed.
Southampton continued to boss matters over the closing stages of the first half but neither side had created much in the final third.
That changed within 38 seconds of the restart as David Murphy burst down the left and found King, whose strike was well palmed around a post by Davis.
Saints' recent signing Billy Sharp was introduced for his debut just minutes into the second half, but it was Davis who was soon at the centre of matters once again as he saved from N'Daw.
Myhill was still to make a stop as Saints failed to capitalise on a defensive mix-up by the hosts with 25 minutes remaining.
The closing stages were largely uneventful until Fox was shown a second yellow for a foul on Chris Burke with seven minutes remaining.
Yet Chris Hughton's side were unable to make their numerical advantage count.
