George Saville took advantage of a static Birmingham backline to slot home Boro's second goal in four first-half minutes
Middlesbrough moved up to sixth in the Championship after coming from behind to hand Birmingham City their third straight defeat.
The Blues started well and went in front when Maxime Colin lashed home a loose ball inside the penalty area.
But the visitors scored twice in four minutes through Britt Assombalonga and George Saville to lead at the break.
Keeper Neil Etheridge fumbled a cross into his own goal and Lewis Wing's long-range effort wrapped up the win.
- Relive Saturday's EFL action
Birmingham almost took the lead after only three minutes when Scott Hogan headed wide, but they didn't have to wait long for the opener.
Colin scored his first goal in 14 months when Boro failed to deal with a cross, allowing the Frenchman to fire home from close range.
Hogan went close to doubling the advantage after 24 minutes but his shot was well saved by the legs of Marcus Bettinelli.
The Blues were made to pay shortly afterwards when Assombalonga levelled matters, finishing well from Marc Bola's cutback.
Boro went in front when Marvin Johnson fired in a low cross and George Saville took advantage of a static Blues defence to turn the contest on its head after half an hour.
With the game still in the balance, Blues goalkeeper Etheridge made a horrendous error to allow the visitors to score a third.
Attempting to claim a routine corner, the ex-Cardiff man fumbled the ball over his own head and could only watch as the ball nestled in the far corner.
Wing's long-range effort settled matters with eight minutes let as Neil Warnock's men inflicted a heavy defeat on former Boro boss Aitor Karanka.
Boro boss Neil Warnock told BBC Tees:
"Marcus made a good save with his feet at 1-0 and then we got the equaliser and that was more like us. We worked hard, we closed them down and they didn't create anything apart from the long throws. We really played on the front foot today.
"I was delighted with a lot of people today and a there were a lot of pluses. You don't always get what you deserve but today we did.
"I thought we could have had more but I was just pleased with the way they played. We were right on top of our game today and I'm sure the fans would have loved it watching that up north."
- Line-upsMatch StatsLive Text
Line-upsBirmingham
- 30Etheridge2Colin4Roberts12Dean3Pedersen8ClaytonSubstituted forSunjicat 45'minutes19San JoséSubstituted forKieftenbeldat 45'minutes17SánchezSubstituted forLekoat 62'minutes23ToralSubstituted forJutkiewiczat 61'minutes11BelaSubstituted forGardnerat 62'minutes9Hogan
Substitutes
- 1Prieto6Kieftenbeld10Jutkiewicz14Leko15Clarke-Salter20Gardner25Dacres-Cogley34Sunjic35Halilovic
Middlesbrough
- 1Bettinelli2Dijksteel6Fry17McNair27Bola5Morsy8Wing7Tavernier22Saville3JohnsonSubstituted forSpenceat 75'minutes9AssombalongaSubstituted forAkpomat 83'minutes
Substitutes
- 10Akpom15Wood18Watmore24Folarin29Spence31Brynn32Stojanovic33Coulson37Jones
Referee:Steve MartinMatch StatsHome TeamBirminghamAway TeamMiddlesbroughPossessionHome54%Away46%ShotsHome9Away6Shots on TargetHome2Away4CornersHome4Away2FoulsHome17Away10Live TextPost update
Match ends, Birmingham City 1, Middlesbrough 4.
90'+3'Full Time
Second Half ends, Birmingham City 1, Middlesbrough 4.
90'+2'Post update
Corner, Birmingham City. Conceded by Sam Morsy.
90'+1'Post update
Foul by Gary Gardner (Birmingham City).
90'+1'Post update
Sam Morsy (Middlesbrough) wins a free kick in the defensive half.
90'Post update
Foul by Harlee Dean (Birmingham City).
90'Post update
Chuba Akpom (Middlesbrough) wins a free kick in the defensive half.
89'Post update
Corner, Birmingham City. Conceded by Patrick McNair.
87'Post update
Attempt missed. Jonathan Leko (Birmingham City) right footed shot from outside the box is too high following a set piece situation.
85'Post update
Attempt missed. Kristian Pedersen (Birmingham City) header from the centre of the box is too high. Assisted by Gary Gardner with a cross following a set piece situation.
85'Post update
Maikel Kieftenbeld (Birmingham City) wins a free kick on the right wing.
85'Post update
Foul by Lewis Wing (Middlesbrough).
84'Post update
Offside, Middlesbrough. Djed Spence tries a through ball, but Chuba Akpom is caught offside.
83'Substitution
Substitution, Middlesbrough. Chuba Akpom replaces Britt Assombalonga.
82'goalGoal!
Goal! Birmingham City 1, Middlesbrough 4. Lewis Wing (Middlesbrough) right footed shot from outside the box to the top left corner. Assisted by Marcus Tavernier.
77'Post update
Foul by Lukas Jutkiewicz (Birmingham City).
77'Post update
Patrick McNair (Middlesbrough) wins a free kick in the defensive half.
76'Post update
Attempt missed. Harlee Dean (Birmingham City) left footed shot from outside the box is high and wide to the left. Assisted by Maikel Kieftenbeld.
75'Substitution
Substitution, Middlesbrough. Djed Spence replaces Marvin Johnson.
71'Post update
Offside, Middlesbrough. Marvin Johnson tries a through ball, but Britt Assombalonga is caught offside.
Page 1 of 5rewindpreviousNavigate to the next pagenextNavigate to the last pageforward
- Documentaries Like Nowhere Else: From inspiration to infamous, the story of Lance ArmstrongComedy Like Nowhere Else: Give Kurupt FM a go with the People Just Do Nothing box set
Source: bbc.com