A fourth defeat in five league games pushed Barnsley closer to the drop as they now sit nine points adrift of safety.
After winning four out of seven games in all competitions the Reds have subsequently failed to win any of the next six.
Barnsley have now lost three of their last six Oakwell meetings with Birmingham however this is the first time since 2001-2002 that the Blues have completed a league double over the Reds.
As stated above Barnsley have lost back to back games against Birmingham, prior to this they were unbeaten in five meetings (W3 D2)
Barnsley's wretched midweek run continues as they have now won only one of their last 21 league matches played on Tuesdays - a 4-0 League One away win at Rochdale in August 2018.
They have lost three of their four Tuesday night league games in 2019-2020 - two of those defeats have been against Birmingham, whilst also drawing two and losing one on a Wednesday.
Since the Rochdale win they have failed to win any of their last 11 Tuesday matches (D6 L5) whilst in the second tier they have failed to win any of the last 13 matches on a Tuesday since a 4-2 win at Burton in October 2017 (D4 L9)
They have now also failed to win any of their last 52 Championship matches in which they have conceded the first goal, (D11 L41) since defeating Leeds 3-2 three years ago (21st January 2017)
Prior to this game Birmingham had won only three of their last 18 away league matches in Yorkshire - and none out of four (D2, L2) this season.
Barnsley have now conceded the opening goal in six successive games for the first time this season and the first time since November/December 2017 (also six)
Clark Oduor was hauled off by Gerhard Struber after just 27 minutes, the earliest change in a game since Mike Bahre was subbed at Derby after 26 minutes at the start of January.
Callum Styles was then replaced at the break, the first time two changes had been made before the start of the second half since Struber's first game in charge, at Blackburn in November when he made two half time switches.
This was the tenth Barnsley league match to be goal-less at half time this season, and Barnsley have failed to go on to win any of them (D4 L6)
Barnsley failed to score at Oakwell for only the third time in the Championship this season (also against Leeds and Preston) - it earnt Birmingham their fifth league clean sheet of the season (and first since October) - two of which have come against Barnsley.
It is the first time Barnsley have failed to score in both league games in a season against Birmingham since 1998-1999 when both encounters finished 0-0.
Barnsley have only won four matches at Oakwell this season, they have won less home games than anybody else in the Championship this season with Scott Hogan's goal the 31st they have conceded in front of their own supporters - the most home goals conceded in the division.
To put it into perspective, when the Reds were relegated in 2017-2018, when they endured their longest ever winless home run, they would concede 32 goals in their 23 matches.
Barnsley had 64% ball possession in the game - it is their joint highest amount this season, doing so on three occasions, two of which have occurred against Birmingham. The other was at Hillsborough, meaning Barnsley have lost all three times and failed to score in all three.
For the third time in four league games there were only six shots on target in a Barnsley game.
40. Brad Collins
2. Jordan Williams
6. Mads Andersen
7. Jacob Brown
9. Cauley Woodrow
18. Michael Sollbauer
20. Callum Styles
22. Clark Oduor
27. Alex Mowatt (C)
28. Elliot Simoes
14. Kilian Ludewig (for Oduor 27)
10. Mike-Steven Bähre (for Styles 45)
16. Luke Thomas (for Simoes 70)
4. Kenny Dougall, 13. Jack Walton, 19. Patrick Schmidt, 24. Aapo Halme
1. Lee Camp
3. Kristian Pedersen
4. Marc Roberts
5. Maxime Colin
10. Lukas Jutkiewicz (c)
14. Jake Clarke-Salter
15. Jefferson Montero
20. Gary Gardner
22. Jude Bellingham
34. Ivan Sunjic
40. Scott Hogan
11. Jeremie Bela (for Montero 70)
12. Harlee Dean (for Jutkiewicz 86)
2. Wes Harding (for Bellingham 88)
7. Daniel Crowley, 27. Connal Trueman, 33. Cheick Keita, 44. Caolan Boyd-Munce.
Birmingham manager Pep Clotet said:
"A win is always very welcome. It was a very difficult game to play because Barnsley were desperate for the points and the conditions were not the best for football. I'm very happy to see that the team can adapt.
"We knew that whoever would score first would have a big chance to win.
"We're very close to our first goal of the season: to stay in the league."
Sky Bet Championship results
TUESDAY 11TH FEBRUARY 2020
BARNSLEY (24th) 0-1 Birmingham City (14th)
Blackburn Rovers (9th) 3-0 Hull City (15th)
Brentford (4th) 1-1 Leeds United (2nd)
Nottingham Forest (5th) 0-1 Charlton Athletic (19th)
Swansea City (10th) 0-0 Queens Park Rangers (17th)
Wigan Athletic (22nd) 2-2 Middlesbrough (18th)
Moukoudi og 76
WEDNESDAY 12TH FEBRUARY 2020
Bristol City (7th) 3-2 Derby County (13th)
Huddersfield Town (20th) 0-3 Cardiff City (8th)
Luton Town (23rd) 1-0 Sheffield Wednesday (12th)
Millwall (11th) 1-1 Fulham (3rd)
Reading (16th) 1-2 West Bromwich Albion (1st)
Puscas pen 11
Costa Pereira 26
Stoke City (21st) 0-2 Preston North End (6th)
Barnsley lie in 24th place in the Sky Bet Championship with 25 points from 32 games. We are 28 points outside the Play-Offs, 31 points outside the Automatic Promotion Places, 37 points outside First Place and 9 points inside the Relegation Zone.
Up to 12/2/20
On The Road:
Sky Bet Championship Matchday Thirty Three: Fulham v Barnsley, Saturday 15th February 2020. Kick-Off: 3pm
Sky Bet Championship Matchday Thirty Four: Barnsley v Middlesbrough, Saturday 22nd February 2020. Kick-Off: 3pm