Barnsley won for just the third time in 20 outings in all competitions - two of those wins have come against Birmingham.
The Reds also ended a club record run of 18 games without managing to score more than once in a game - the last team they had scored more than once against prior to yesterday? Birmingham.
Those two victories over the Blues gave the Reds their first league double against the Second City outfit since 1946-1947 and only their second ever.
Oliver McBurnie now has three goals from three starts for Barnsley, he is the first Reds player to score a brace since Tom Bradshaw at Millwall in September.
He could have been the first Barnsley player to score a hattrick since Sam Winnall in January 2016 but missed a first half penalty.
It is only the third penalty Barnsley have been awarded this season, it is the first missed since October 2016 when Sam Winnall was denied against Bristol City.
As well as being the first time Barnsley scored more than once since November, it is the first time they have scored two first half goals since the 31st October in the 4-2 win at Burton.
It is only the second time this season the Reds have led by two goals at half time in the Championship, the only occasion being the 3-0 win over Sunderland in August.
This was Barnsley's fourth away win of the season and they have so far picked up 16 points on their travels - in contrast to just three wins and 15 points at Oakwell.
Barnsley are now unbeaten in five meetings with Birmingham (W3 D2) with the same recent record at St Andrews.
The Reds have also kept clean sheets in three of the last five visits, scoring 12 times themselves.
It is the first time they have kept clean sheets in both league meeings with Birmingham since 1998-1999 when both meetings finished 0-0.
This was also a big win for goalkeeper Nick Townsend. He made his 14th start for the Reds yesterday and ended up on the winning side for just the fourth time (and first since September 2015)
It was also only the second time Townsend has kept a clean sheet for Barnsley, the other occasion being a 2-0 League One win over Gillingham - the last time he was on the winning side.
Brad Potts started a game for the first time since the 20th January, the Reds have lost only one of the last four Championship matches that he has started.
It was also a first start since October for Adam Jackson following a knee injury - the Reds have lost only one of the last five matches he has started.
Yesterday was the first time Tom Bradshaw did not start a game since the New Year's Day win at Sunderland, and the first time he did not get any minutes on the pitch since the 5th November 2016 - he had appeared in 68 games in a row in all competitions.
Birmingham have now lost their last four Championship games, failing to score each time - their longest losing run without scoring since October 2005 (also five), en route to relegation from the Premier League.
The Blues have failed to score in 18 different Championship games this season, more than any other side in the division.
No Barnsley player was shown a card for the first time in nine matches in all competitions.
Connor Mahoney (for Thiam 60)
Christoph Knasmullner (for McBurnie 77)
Matty Pearson (for Gardner 87)
Adam Davies, Dimitri Cavare, George Moncur, Tom Bradshaw.
David Stockdale, Maxime Colin, Carl Jenkinson, Marc Roberts, Harlee Dean, Craig Gardner, Jeremie Boga, Jacques Maghoma, Cheikh N'Doye, Che Adams, Sam Gallagher.
Jota (for N'Doye 66)
Cohen Bramall (for Jenkinson 83)
Connal Trueman, Josh Dacres-Cogley, Michael Morrison, Jason Lowe, Lukas Jutkiewicz.
Birmingham manager Steve Cotterill said:
"They're unrecognisable from the team they were a month ago and the difference is confidence.
"We looked nervous as anything in the first half and there wasn't enough players getting on the ball and you can't have that.
"I don't think we are strong enough as a squad and we didn't strengthen in the window and I think we could have done with doing that. We've had a few injuries and suspensions and it's thrown us out all over the place.
"It's not nice to take the stick I take but if it's someone else managing the team in a month's time then they're in the same situation because it'll be the same players going out on the pitch."
Sky Bet Championship results:
Friday 23rd February 2018:
Hull City 1-0 Sheffield United
Birmingham City 0-2 BARNSLEY
Burton Albion 0-1 Millwall
Leeds United 1-0 Brentford
Norwich City 0-0 Bolton Wanderers
Preston North End 0-1 Ipswich Town
Queens Park Rangers 2-5 Nottingham Forest
Luongo 68 Tomlin 37,47, Lolley 51, Cash 76, Berereton 90+1
Reading 3-3 Derby County
Kelly 16 Palmer 6, Keogh 35, Lawrence 46
Sheffield Wednesday 2-4 Aston Villa
Clare 14 Grabban 21, Whelan 67, Hourihane 87, Snodgrass pen 90+3
Fulham 2-0 Wolverhampton Wanderers
Sunday 25th February 2018:
Cardiff City 1-0 Bristol City
Barnsley lie in 21st place in the Sky Bet Championship with 31 points from 33 games.
We are 23 points outside the Play-Offs, 36 points off the Automatic Promotion Places, 42 points off First place and 1 point above the Relegation Zone.
Up to 25/02/18
On The Road:
Sky Bet Championship Matchday Thirty Four: Hull City v Barnsley: Tuesday 27th February 2018. Kick-Off: 7:45pm
Sky Bet Championship Matchday Thirty Five: Barnsley v Norwich City, Saturday 3rd March 2018. Kick-Off: 3pm