Gary Taylor-Fletcher grabbed the only goal as Blackpool secured a shock victory at high-flying Birmingham.
Taylor-Fletcher drilled the winner past Maik Taylor after being teed up by Keith Southern on 47 minutes.
Blackpool's victory margin could have been greater against an out-of-sorts Blues but Taylor made super saves to deny David Vaughan and Ben Burgess.
The home side barely threatened with Cameron Jerome and Kevin Phillips missing half-chances.