Doncaster defender George Friend has completed his move to Middlesbrough for an undisclosed fee.
The 24-year-old has passed a medical and signed a three-year deal.
Boro manager Tony Mowbray said: "I think George will be a good signing for us.
"He's a versatile player who can play at centre-half and left-back. He's very athletic and very mobile and has all the attributes you look for in a player.
"He's going to create really good competition to get into our side."
Friend is hoping his spell at Boro will help him win the chance to play Barclays Premier League football.
He said: "Middlesbrough finished just outside the play-off places last season and Tony Mowbray is building a really strong squad here."