The 23-year-old midfielder extended his contract at Stamford Bridge until the summer of 2019, having become an integral part of the team which tops the Premier League.
The Brazilian has extended his deal with the west Londoners until 2019 and says that he is delighted to be staying in the Premier League.
He told the club’s official website: “I am so happy because I love playing for Chelsea and living in England.
“I have enjoyed playing here for two years, and now I have five more, so I am very happy.”
Oscar has started 13 of the Blues’ 17 games across all competitions so far this season, his three goals and two assists in the Premier League helping to propel Jose Mourinho’s side to the top of the table.
He has made 126 appearances for the club since signing from Internacional in 2012.