The Brazilian winger joined the Cottagers on loan until January in the summer but has extended his temporary stay at Fulham.
The 22-year-old has made just three first team appearances for Chelsea since joining in 2012 and has already on his fifth loan spell away from the club.
The Brazil U-23 international has played 17 games for Slavisa Jokanovic's side this season scoring four goals.
Piazon will try to help Fulham win promotion to the Premier League, most likely via the play-offs as the west London club sit two places and six points of the top six in the Championship.