The blues have been rewarded for their dramatic late victory against Leicester with a trip to the Olympic Stadium.
Chelsea secured passage to round four courtesy of an emphatic 4:2 victory over Leicester and will now tackle the Hammers in an all Premier League affair for a place in the last eight.
Westham meanwhile needed a stoppage time goal from Dimitri Payet to book a place in this round.
The fixture will be played on the week commencing on October 24.

Go Blues