QPR head coach Chris Ramsey will make "every effort" to keep striker Charlie Austin at Loftus Road.
Filippo Inzaghi wants to keep on-loan Chelsea midfielder Marco van Ginkel at AC Milan for another season.
This season Tello has made 16 appearances in all competitions for Barca, having represented Spain at this summer's Olympics.
A Barcelona statement read: "Barcelona announce they have reached an agreement with the player Cristian Tello to extend his contract until June 30, 2016. His buy-out clause has been set at 10 million euros.
"The player will sign his contract on Monday, December 17, in the Barcelona offices."