Following the arrivals of Jordan Archer, Yannick Bolasie and Darnell Fisher, Boro added former Cardiff winger Nathaniel Mendez-Laing and Fulham midfielder Neeskens Kebano to their ranks on transfer deadline day.
The Teessiders also allowed Nathan Wood and Lewis Wing to leave the club on loan, while playmaker Patrick Roberts was allowed to cut short his loan spell, allowing the Manchester City man to join Derby for the second half of the campaign.
While there weren’t as many big-money deals compared to previous windows, there were still plenty of moves around the second tier as clubs finalised their squads.
We've taken a look at every deal which was completed in the Championship and how Boro’s rivals fared:
9. Derby
INS: Patrick Roberts (Manchester City, loan) Teden Mengi (Manchester United, loan), George Edmundson (Rangers, loan), Beni Baningime (Everton, loan), Lee Gregory (Stoke, loan) OUTS: Mike te Wierik, Duane Holmes, George Evans, Morgan Whittaker Photo: Andrew Kearns - CameraSport
10. Huddersfield
IN: Rolando Aarons (Newcastle), Richard Keogh (MK Dons), Duane Holmes (Derby), Danny Grant (Bohemians), Sorba Thomas (Boreham Wood), Jayson Leutwiler (Fleetwood) OUTS: Ben Hamer, Adama Diakhaby Photo: George Wood
11. Luton
INS: Kal Naismith (Wigan) Tom Ince (Stoke, loan) Elijah Adebayo (Walsall), Gabriel Osho (free) OUTS: Peter Kioso (loan) Photo: Julian Finney
12. Middesbrough
INS: Jordan Archer (free), Yannick Bolasie (Everton, loan), Darnell Fisher (Preston), Nathaniel Mendez-Laing (free), Neeskens Kebano (Fulham, loan) OUTS: Dejan Stojanovic (loan), Thomas Mejias, Lewis Wing (loan), Patrick Roberts, Nathan Wood (loan) Photo: Richard Heathcote