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:
5. Brentford
INS: Saman Ghoddos (Amiens) Winston Reid (West Ham, loan) OUTS: Said Benrahma, Halil Dervisoglu (loan) Photo: Clive Rose
7. Cardiff
INS: Max Watters (Crawley), Perry Ng (Crewe), Jonny Williams (Charlton) OUTS: Greg Cunningham (loan), Robert Glatzel (loan), Gavin Whyte (loan), Filip Benkovic Photo: Harry Trump
8. Coventry
INS: Matty James (Leicester, loan), Viktor Gyokeres (Brighton, loan), Josh Reid (Ross County), Fabio Tavares (Rochdale) OUTS: Gervane Kastaneer (loan), Marcel Hilßner (loan) Photo: Harry Trump