Scott Hogan's hat-trick clinched a 3-2 victory for Birmingham to continue West Brom's indifferent start to the season at The Hawthorns.
Striker Hogan put City ahead early in each half sandwiching Jed Wallace's equaliser before adding a classy third to make it successive away wins for City.
Substitute Brandon Thomas-Asante made it 3-2 with a late penalty but Albion could not force a further equaliser as Birmingham made it successive away victories and won at The Hawthorns for the first time since August 2005.
After a 15-minute delay due to traffic congestion and then an impeccably observed minute's silence and the national anthem in tribute to the late Queen, the game got under way.
Blues had the first chance when Troy Deeney's fierce first-time drive cannoned off a stanchion behind the goal.
Albion returned fire with a chance for Karlan Grant but Kyle Bartley's flick-on from John Swift's corner was slightly too high and he nodded wide.
Blues threatened again through Tahith Chong but the former Manchester United youngster blazed well over the bar.
The visitors looked really lively and took a 14th-minute lead. Hogan supplied a cool, low finish across goalkeeper David Button after Juninho Bacuna's through ball beat the offside trap.
Albion tried to hit back and Wallace's low angled drive was turned around the post by goalkeeper John Ruddy before Bartley sent a looping header over from another Swift corner.
The Baggies were level in the 23rd minute. Jayson Molumby's neat through ball evaded the sliding Josh Williams and Wallace calmly slotted through Ruddy's legs.
Molumby was not far away with a dipping, swerving drive that sailed a foot over the bar before Swift's similar effort was palmed upwards by Ruddy.
Blues regained the lead in spectacular style in the 54th minute. Hogan sidefooted home his second of the game and fourth of the season, but it owed so much to Bacuna, who started the move by winning the ball from a West Brom corner
before taking Troy Deeney's pass and racing clear, prior to supplying the cross.
Hogan completed his hat-trick when he latched on to a superb through ball from Deeney on the left and cut inside before poking the ball through Button's legs at the near post.
Thomas-Asante reduced the arrears with an 83rd-minute penalty after he was brought down by Dion Sanderson, although it looked like it was outside the area.
Albion continued to dominate possession but Blues defended well to hold their Midlands rivals at bay.
What the managers said...
West Brom's Steve Bruce: "We didn't take part in the game until the last 20 minutes. In a big derby we were found short. We didn't win a challenge and we didn't deal with Troy Deeney and the physicality of Birmingham. We were nowhere near where we should be. Individual errors are something you can't fix.
"The concentration of the defenders was awful and the goals were something you'd see on the schoolboy pitch with 11-year-olds. When you defend as hideously as that, you're in for a poor evening. It was awful. What we witnessed in the first hour was scandalous."
Birmingham's John Eustace: "Scott Hogan is a top, top striker. The one thing I was excited about coming here was that I've worked with Scott at international level and I know what he can bring to the Championship. You don't have moves like he's had if you're not a top striker. The lad just needs confidence but you can see he's a top, all-round player.
"The way he took his hat-trick was three different finishes and it was brilliant."