The club has completed a move for Charlton Athletic’s highly-rated defender Anfernee Dijksteel.
The former Dutch Under-20 international has put pen to paper on a 3-year contract after finalising his switch at Rockliffe on Wednesday.
The 22-year-old arrives having clocked up 59 appearances for Charlton after joining the club from the Nike Academy.
Boro head coach Jonathan Woodgate said: “Anfernee is another young player who fits the mould of what we want at this club. He’s the type of footballer I like. I like the way he gets forward and the way he gets back, he’s very athletic.
“I’ve watched him and I like what I’ve seen. I’ve done a lot of work on him, and he’s my number one choice.”
Dijksteel, who played for Charlton in their opening day win at Blackburn, will train with his new team-mates for the first time on Wednesday.
He will wear the no.2 shirt this season.