The two West London sides met in the Premier League a fortnight ago and will now go head to head in the cup at Brentford Community Stadium in the week beginning Monday 20th December.
The Bees reached this stage by overcoming Stoke City 2-1 on Wednesday night, that after a 7-0 home win over Oldham and a 3-1 victory hosting Forest Green Rovers.
Chelsea joined a round further into the competition and have been taken to penalties in both of their last two games. The first, winning 4-3 over Aston Villa after a 1-1 draw in normal time. The Blues then needed spot-kicks again after securing the same 1-1 scoreline against Southampton, Kepa Arrizabalaga the hero once more in a 4-3 win.
The league match finished 1-0 to Chelsea thanks to a Ben Chilwell strike in the first half. Goalkeeper Edouard Mendy put in a man of the match performance to help Thomas Tuchel's side to three points in a final 20 minutes that could have seen any number of Bees players on the scoresheet.
Fixture confirmation and ticket details will be released in due course.