Chelsea are set to sign 17-year-old Estevao Willian from Palmeiras after they agreed an initial fee of 34m euros (£29m) for the winger.
The deal does include performance related add-ons for one of the most highly-rated young players in Brazil.
It is another large outlay by Chelsea, but continues their strategy of trying to sign the best young talent in the world.
The Blues have brought in a number of young players from South America in recent times, including Andrey Santos, Deivid Washington, Angelo and 17-year-old Ecuadorian forward Kendry Paez, who will arrive in 2025 from Independiente del Valle.