Craig Gardner was the match winner for Birmingham in a dramatic semifinal second leg at St. Andrew's, firing home from 25 yards in the fourth minute of extra time to earn the Midlands club a 4-3 aggregate win.
Carlton Cole scored a stunning goal in the 31st to put West Ham 3-1 up in the two-legged series but Birmingham took the game into extra time thanks to second-half goals by Lee Bowyer and Roger Johnson.
The Blues, whose only major trophy came when they won the League Cup in 1963, will be underdogs when they play Arsenal at Wembley on Feb. 27.
Arsenal qualified for the final by beating second-tier side Ipswich 3-0 in the second leg of their semifinal, winning 3-1 on aggregate.
