Birmingham picked up the point they needed to effectively secure their place in the play-offs despite a late rally from Brighton in a 1-1 draw.
Substitute Nathan Redmond put the visitors ahead in the 69th minute of Saturday's Championship clash, but Ashley Barnes grabbed the leveller for Albion in the closing stages.
Chris Hughton's Blues were not at their best but they are now unbeaten in their last eight matches, although they slipped a place to fifth following Blackpool's win over Burnley.
Yet it was Brighton, looking to end their first season at the Amex Stadium on a high, who almost took an 11th-minute lead.
A clever ball from former Spain midfielder Vicente Rodriguez sent Will Buckley through but the winger's shot forced a fine block from Blues goalkeeper Colin Doyle, with the ball looping up over the crossbar and onto the top of the net.
Hughton sent teenage winger Redmond on with just half an hour gone as Morgaro Gomis was sailing close to the wind after an early booking.
The move almost paid immediate dividends as Birmingham's best chance of the first half fell to the teenager, who cut inside before fizzing his shot across goal and just wide of Peter Brezovan's post.
At the other end, the visitors were almost caught out by a deep Vicente free-kick which found Joe Mattock at the far post, but the left-back's volley crashed into the side-netting.
Doyle was in action again two minutes after the interval with a smart save to keep out Alan Navarro's drive from the edge of the area.
Mattock then fashioned another chance for himself on the overlap but his shot flew over the crossbar.
Hughton made another change, replacing the ineffective Erik Huseklepp with Andros Townsend, and that almost proved an inspired substitution after the winger fizzed a shot narrowly wide within moments of coming on.
However, it was Hughton's first-half sub who eventually broke the deadlock.
Marlon King was the architect with a powerful run at the Brighton defence before laying the ball off to Redmond, who fizzed a low drive past Brezovan and into the bottom right-hand corner from 20 yards.
Townsend came close to doubling City's lead with a 25-yard effort which was well saved by the diving Brezovan.
However, Brighton went in search of an equaliser and Doyle got down well to deny Craig Mackail-Smith.
But Doyle could not prevent Barnes sidefooting in from Inigo Calderon's cut-back with six minutes remaining to snatch a point for the hosts.