Piazon has signed a pre-contract agreement with the London outfit 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 until then he will continue to represent Sao Paulo.
He is regarded in his homeland as one of the brightest young prospects and has been compared to Real Madrid star Kaka.
The emerging talent finished top scorer in the South American Under-15 Championships in 2009, netting ten goals, and he is currently representing Brazil in the under-17 tournament.
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 Piazon was named player of the tournament.