Jordan Rhodes, Julien de Sart, Ritchie De Laet all arrived on deadline day while Gaston Ramirez and Kike Sola joined earlier in the month.
The transfer window also saw the departures of loan men Diego Fabbrini and Fernando Amorebieta.
Here's all the content that you need about our business in January, how it happened and who's who. Read, watch, and enjoy...
WATCH: Aitor Karanka gives his verdict on the transfer window
READ: Jordan Rhodes signs
FACT FILE: All you need to know about Jordan Rhodes
WATCH: Here's all Jordan Rhodes' goals from this season
READ: Jordan Rhodes - I can't wait to get started
READ: Ritchie De Laet signs for Boro
FACT FILE: All you need to know about Ritchie De Laet
READ: Julien De Sart signs
READ: Gaston Ramirez Joins the club
READ: Kike Sola Signs Up
READ: Fernando Amoerbieta returns to Fulham
READ: Diego Fabbrini loan is ended