Alex McLeish's troops looked to be heading to defeat after the home side were rewarded for a flying start by Russian Diniyar Bilyaletdinov's early strike.
However, the Blues weathered a first-half onslaught at Goodison Park equalising through Larsson in the 22nd minute, before battling treacherous weather conditions to hold on after the break.
Birmingham had barely settled before finding themselves one down in the fifth minute when midfielder Bilyaletdinov fired home following striker Louis Saha's flick on.
Saha thought he had gone from provider to scorer moments later lashing home after being put through by Tim Cahill - however the former Manchester United frontman was deemed to be offside.
Everton were threatening to run riot at Goodison Park and former Millwall midfielder Cahill had a glorious chance in the 11th minute but his first-time shot sailed narrowly over.
Disaster struck for the Toffees after 22 minutes when completely against the run of play Ecuadorian Christian Benitez found space in the hosts box and picked out Larsson, who calmly slotted home.
Birmingham gradually started to grab a foothold on the game at, but still the Toffees looked more dangerous after the interval, with Cahill twice going close as the rain poured.
Firstly the Australia international was denied at the near post by Birmingham's Roger Johnson following Leighton Baines' teasing cross.
Then, after Baines and Marouane Fellaini combined to set up Cahill, again his neat flick was cleared away by the ever-present Johnson at the back.
Nothing would fall for Everton and after Birmingham stuck all eleven men behind the ball Saha volleyed wide and headed a free-kick over.
The Toffees were given four minutes of added time to find the net, but failed to do so as the visitors got the point their resolute display deserved.