Blackpool boss Lee Clark has signed Manchester United midfielder Joe Rothwell on loan until the end of the season.
Newcastle midfielder Moussa Sissoko is happy to stay at the club, despite rumours he is a target for Arsenal.
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."