The Brazil international defender has passed his medical in London to return to Stamford Bridge only two years after leaving the club for the French champions.
Chelsea have completed the signing of Brazil international David Luiz from Paris Saint-Germain for £38m (€45m).
The 29-year-old returns to Stamford Bridge just two years after leaving Chelsea, who opened talks with their ex-player on Tuesday.
Luiz has signed a contract and completed a medical according to sources close to Goal but details have yet to emerge over the length of the deal.
PSG have decided not to sign a replacement for Luiz despite only having three recognised centre-backs in Thiago Silva, Marquinhos and Presnel Kimpembe, with Serge Aurier capable of deputising.
Chelsea have officially announced the signing of Marcos Alonso from Fiorentina while they also have the option of signing Aymen Abdennour on loan from Valencia.
Meanwhile, Juan Cuadrado has also officially left Chelsea for Juventus on a three-year loan with the option to buy.