Blues forward Scott Hogan scored the only goal of the game in the 26th minute as former Boro boss Aitor Karanka claimed a win over his former club.
Our Boro writer Joe Nicholson has dished out his marks from the match– scroll down and flick through the pages of our picture gallery to see how each player fared:
5. Marc Bola - 5
Made a couple of runs forward but had his hands full defensively at times. 5 Photo: Clive Brunskill
6. Sam Morsy - 5
Unfortunate not to equalise with a first-half header which hit the bar and post. Spent most of the first half chasing the ball as Birmingham controlled the midfield area. Replaced at half-time. 5 Photo: Alex Pantling
7. George Saville - 5
Looked a little off the pace in midfield as Boro struggled to get forward. 5 Photo: Getty Images
8. Marcus Tavernier - 6
Saw more of the ball in the second half after moving to a central position. 6 Photo: George Wood