The US hip-hop duo were due to play on the Radio 1/NME Stage on August 24 in Reading and August 25 in Leeds.
Hadouken! have stepped in to replace the rappers and will perform at the festivals instead, reports NME.
There is currently no explanation behind Chiddy Bang's cancellation at both venues.
Hadouken! are currently working on their third studio album, which will contain new single 'Bad Signal'.
The Cure, Foo Fighters and Kasabian will headline this year's Reading and Leeds Festivals.
Paramore, The Vaccines, At The Drive-In, You Me At Six and Bombay Bicycle Club are also among the longlist of acts set to perform.
Watch the Hadouken! 'Parasite' music video below: