The 29-year-old arrived in London this evening to undergo a medical and agree personal terms.
A Chelsea statement read: “Chelsea Football Club and Paris Saint-Germain have agreed terms for the transfer of David Luiz back to London.
“The move is now subject to him agreeing personal terms and passing a medical.”
Chelsea first signed Luiz in January 2011 from Benfica for £21m and he made 143 appearances in his three years at the club, scoring 12 goals.
PSG signed him for £50m in 2014 after he was deemed surplus to requirements by former Blues boss Jose Mourinho.
Antonio Conte had made signing a new centre back a key target this summer but saw moves for AC Milan’s Alessio Romagnoli and Napoli’s Kalidou Koulibaly fail.
Chelsea owner Roman Abramovich was pushing the deal to bring Luiz back to West London.
PSG decided to cash in on the centre-back as he was no longer regarded as first choice under the French champions’ new boss Unai Emery.
The former Sevilla manager sees Luiz’s compatriot Marquinhos as his preferred partner to captain Thiago Silva.
Marquinhos had been in demand over the summer with both Chelsea and Manchester United enquiring about his availability.
But PSG had no intention of selling the 22-year-old which saw Chelsea turn their attentions to Luiz.