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:
17. QPR
INS: Charlie Austin (West Brom, loan) Jordy de Wijs (Hull, loan), Stefan Johansen (Fulham, loan), Sam Field (West Brom, loan), Joe Walsh (Gillingham) OUTS: Bright Osayi-Samuel, Joe Lumley (loan) Photo: Lewis Storey
18. (7th) Reading - 69 points
INS: N/A OUTS: Sam Walker (loan), Sam Smith (loan) Photo: Naomi Baker
19. Rotherham
INS: Ryan Giles (Wolves, loan), Lewis Wing (Middlesbrough, loan), Josh Vickers (free) OUTS: Mickel Miller (loan), Kyle Vassell (loan), Billy Jones (loan), Adam Thompson Photo: Catherine Ivill
20. Sheffield Wednesday
INS: Andre Green (free), Sam Hutchinson (FC Pafos) OUTS: Aden Flint, Izzy Brown Photo: Lee Parker - CameraSport