Bournemouth maintained their amazing record at St Andrew's as two late second-half goals ended Birmingham City's unbeaten start to the season.
On a ground where the Cherries have never lost in 13 visits they looked there for the taking at half-time, having failed to get a single effort on target.
But Scott Parker's side kept their cool with a much-improved display after the break, capped by Dominic Solanke's excellently taken 77th-minute opener, followed by Jaidon Anthony's 87th-minute second to secure the three points.
Bournemouth are one of six unbeaten Championship sides on seven points from three games.