Piazon has signed a pre-contract agreement with the current Premier League champions after the two clubs reached an agreement over the transfer of the player.
The 17-year-old will join Chelsea in January 2012 on a long-term contract and will continue to represent Sao Paulo until then.
The Brazilian joined Sao Paulo in 2003 and is highly regarded in his homeland as one of the brightest young prospects, drawing comparisons to Real Madrid star Kaka.
He is currently representing Brazil in the South American Under-17 Championships and finished top scorer in the 2009 Under-15 Championships with 10 goals.
The player will make the switch to the Premier League having played in England once before, in an under-15 competition held at Old Trafford in which he was named player of the tournament.
The attacker was believed to be close to sealing a move to Juventus and had even trained with the Serie A club in January before Chelsea wrapped up the signing.