The 21-year-old striker had been given a choice between No.11 - formerly used by Bayern Munich signing Thiago - and the No.7 made available by David Villa's departure to Atletico Madrid, reports Xinhua.
"The announcement was made informally via the audio on the club's website."
Neymar is still in Brazil after the Selecao's triumphant Confederations Cup campaign last month. He is scheduled to begin training with his Barcelona teammates July 25.
Meanwhile, Lionel Messi has insisted Neymar will have no problem adapting to his new life at the Camp Nou.
And the four-time Ballon d'Or winner reiterated that he will have no problem playing alongside the former Santos starlet.
"I don't know him personally, but he seems like a good kid," Messi said during a press conference at the Camp Nou. "There won't be any problem with me or anybody else in the dressing room."
"It's a squad full of great people and he won't have any issues adapting on and off the field."