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:
1. Barnsley
INS: Liam Kitching (Forest Green), Carlton Morris (Norwich), Daryl Dike (Orlando City, loan) OUTS: Mike Bahre, Corey Addai (loan), Luke Thomas (loan) Photo: George Wood
2. Birmingham
INS: Rekeem Harper (West Brom, loan), Sam Cosgrove (Aberdeen), Rekeem Harper (West Brom, loan), Yan Valery (Southampton, loan) OUTS: Maikel Kieftenbeld, David Davis, Dan Crowley Photo: Alex Burstow
4. Bournemouth
INS: Jack Wilshere (free), Ben Pearson (Preston), Shane Long (Southampton, loan) OUTS: Dan Gosling, Mark Travers, Jack Simpson, Josh King, Nnamdi Ofoborh (loan) Photo: Naomi Baker