Les Bleus announced on Thursday that they had reached an agreement to take the 21-year defence to Stamford Bridge this after his contract expired in Nice.
He will be sent on loan for next season before returning to Stamford Bridge to take up a first-team spot next summer.
Sarr, who basically plays in the centre defender and is left-handed, has played at the Nice home since the age of five and has become a regular in his first team at 17.
West London had been connected to a resolution to Sarr signal signals in recent days and Chelsea FC boss Granovskaia has now explained why the Blues had chosen to sign it on a five-year contract.
“The opportunity to point out to Malang an opportunity we couldn’t miss,” Granovskaia said in an interview with the Chelsea FC website.
“It’s a wonderful prospect and we’ll look at it a lot during your loan period, hoping you’ll be back to Chelsea soon.
“We are very happy to welcome you to the club today.”
Sarr, who played 119 games and scored 3 goals for Nice, is eligible to play for Senegal thanks to his parents, however, he has represented France under-16 at under-21s and has captained his under-18s.
Chelsea FC has been busy in the summer moving window, with Sarr being the fourth arrival at Stamford Bridge before next season.
The Blues have hired Timo Werner, Hakim Ziyech and Ben Chilwell as Frank Lampard prepares for his stint at Stamford Bridge.
Chelsea FC then showed the signing of Brazilian defender Thiago Silva in a lazy on Friday.
The West London look will begin his Premier League crusade with a Brighton and Hove Albion on 14 September.
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