The club have finalised a loan move for Arsenal striker Folarin Balogun.
The England Under-21 international has joined the club until the end of the season.
Boro fought off competition from a number of clubs to secure the services of the highly-rated young marksman.
Balogun, who has made two Premier League appearances this season, has clocked up 16 in total for the London club and scored twice in five Europa League appearances last time around.
He has also netted 13 goals in 11 PL2 starts this term, along with two goals in the Papa John’s Trophy.
Boro boss Chris Wilder said: “We’re delighted to get Flo in. He’s a player I’ve known about for a long time and we identified him as someone who could come in and improve us in the second half of the season.
“He has great movement, good pace, and he’s a natural finisher. We’re looking forward to working with him.”
The 20-year-old follows Aaron Connolly and Caolan Boyd-Munce into the club as January arrivals.