The Blues have signed the 20-year-old in a deal reported to be worth £25million.
Oscar has signed a five-year contract with the Premier League giants.
A statement on Chelsea’s official website read: “Chelsea football club is delighted to announce the signing of Oscar.”
Oscar is currently in England with the Brazil Olympic squad.
Tottenham had also been linked with the youngster.
“If I go to Chelsea it will be a dream come true,” Oscar revealed earlier this week.
“They are one of the greatest teams in Europe. I am confident I will have a good Olympics and, if I go to Chelsea, I will arrive feeling good.”
