Joao Mendes with his father Ronaldinho
The 18-year-old striker follows in the footsteps of his World Cup-winning father, who had five successful seasons at the Camp Nou.
Mendes terminated his contract at Brazilian Serie B side Cruzeiro to join Barcelona's Under-19 team on trial.
He had kept the identity of his father a secret until he secured a trial and deal with Cruzeiro.
Ronaldinho, 42, now works as an ambassador for Barcelona after retiring from football in 2015.
The flamboyant former forward, a Ballon d'Or winner in 2005, helped the Catalan giants win a Champions League and back-to-back La Liga titles during his spell at the club.
Mendes will be part of Barcelona's famous La Masia academy, which has produced icons such as Lionel Messi, Gerard Pique and current boss Xavi.
-- Courtesy of BBC Sport