The Teessiders have confirmed they have also negotiated personal terms with the 24-year-old.
A statement on Middlesbrough's official website on Friday evening said: "Boro have agreed a fee with Doncaster Rovers for the transfer of defender George Friend.
"He is undergoing a medical and the final details of the transfer are expected to be completed on Monday."
Boro boss Tony Mowbray has already made a series of summer signings including Jonathan Woodgate, Stuart Parnaby, Grant Leadbitter and Emanuel Ledesm
- Doncaster Rovers