Charlie Austin stepped off the bench to bag a dramatic brace as Albion twice came from behind to secure a thrilling 3-2 derby victory over midlands neighbours Birmingham.
Grady Diangana's fifth goal of the season quickly cancelled out Lukas Jutkiewicz's third-minute header amid a frenetic start at a windy St Andrew's.
Blues restored their advantage just minutes after the interval courtesy of Harlee Dean's header.
But it was substitute Austin who made the decisive impact, levelling matters in the 73rd minute with a superb first-time finish from 20 yards shortly after his introduction.
And it was the Baggies marksman who completed the turnaround to secure local bragging rights when he headed home an 81st-minute winner, sending the 2,768 travelling Albion fans into raptures.