Muzzy Carayol is returning from loan at Huddersfield after spending the first half of the season at the John Smith's Stadium.
The winger scored three goals in 15 appearances with the Terriers but manager David Wagner has a surfeit of midfielders at his disposal and Huddersfield have elected to exercise a break clause allowing him to return to Teesside.
Yanic Wildschut is also returning to Boro following a successful six months' loan at Wigan Athletic, where the Dutch winger has scored four goals in 17 appearances.
Meanwhile, three Boro players have extended their existing loans until the end of the season.
Adam Reach will remain at Championship rivals Preston, having scored two goals in 16 league appearances. Bradley Fewster will remain at League Two side York City, where he has scored one goal in four league appearances, and Bradley Halliday will remain at fellow League Two club Accrington, where he has played 11 games.
In terms of outgoings, Bruno Zuculini has returned to Manchester City and Jack Stephens has also been recalled by Southampton.