The young attacker has officially signed off on the deal that will keep him at Camp Nou for three more seasons.
The new contract, which was agreed to last week but only signed on Monday, ties the player to the team until 2016 and includes a 10 million euro release clause.
"I’m very proud and I’m very happy, I’ve dreamed about this since I was a child," Tello said. "I want to return the confidence to those who have confidence in me."
Tello made his first-team debut for Barcelona on Nov. 8, 2011, in a Copa del Rey match against Hospitalet, scoring twice in a 9-0 rout. The 21-year-old La Masia academy product has so far made 23 appearances for the Catalans, scoring five goals in the process.