Kevin Phillips crowned his debut with an injury-time strike that gave Birmingham victory against fellow promotion hopefuls Sheffield United.
Substitute Phillips scored on the turn with seconds left to deny the Blades a draw their performance deserved.
And there was still time for Jon Stead to almost snatch a point when his cross struck a post with Maik Taylor beaten.
Gary Speed and Billy Sharp had also tested Taylor with first-half efforts, but Phillips proved the match-winner.
Birmingham boss Alex McLeish on Kevin Phillips' injury-time winner:
"I am ecstatic. I told them to keep pushing forward in the last couple of minutes.
"Phillips has got the quality and he is a superb finisher and showed it with the goal.
"The tempo was good and we defended much better. There was anxiety on our side as the game went on but that is understandable with it being our first game at home but we held our nerve."
Sheffield United boss Kevin Blackwell:
"It is exceptionally hard to take this loss.
"I don't know how Kevin does it, he had one opportunity and scored.
"I will give Kevin all the credit but I am so frustrated. We were very well organised and they did not give us too many problems.
"But we have put down a marker that we will be tough to beat and hopefully we will get our run of luck later in the season."
Birmingham: Maik Taylor, Parnaby, Martin Taylor, Ridgewell, Murphy, Larsson (Jerome 82), Carsley, Nafti, McSheffrey (Phillips 65), McFadden, Bent (O'Connor 73).
Subs Not Used: Doyle, Queudrue.
Booked: Parnaby, Carsley.
Goals: Phillips 90.
Sheff Utd: Kenny, Jihai, Morgan, Kilgallon, Naysmith, Halford, Tonge, Speed, Quinn, Henderson (Stead 82), Sharp (Webber 61).
Subs Not Used: Cotterill, Spring, Ehiogu.
Booked: Stead.
Att: 24,019
Ref: Keith Stroud (Hampshire).
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