The Blues agreed to sign Piazon from Sao Paulo in March of last year, but could not apply for a work visa until the player's 18th birthday on January 20 of this year.
The terms of the youngster's contract when he arrived in London last summer were undisclosed, but it has now been announced that he has penned a five-and-a-half-year deal.
Piazon joined Chelsea in a deal reportedly worth up to £10 million, and has played in the club's youth and reserve sides this season.
The former Brazil Under-17 international is unlikely to be thrust into the Chelsea first team in the immediate future but is now eligible to feature for the senior side if manager Andre Villas-Boas wishes to select him.
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